Techniques for Arrayed Printing of a Permanent Layer with Improved Speed and Accuracy

ABSTRACT

A repeatable manufacturing process uses a printer to deposits liquid for each product carried by a substrate to form respective thin films. The liquid is dried, cured or otherwise processed to form from the liquid a permanent layer of each respective product. To perform printing, each newly-introduced substrate is roughly mechanically aligned, with an optical system detecting sub-millimeter misalignment, and with software correcting for misalignment. Rendering of adjusted data is performed such that nozzles are variously assigned dependent on misalignment to deposit droplets in a regulated manner, to ensure precise deposition of liquid for each given area of the substrate. For example, applied to the manufacture of flat panel displays, software ensures that exactly the right amount of liquid is deposited for each “pixel” of the display, to minimize likelihood of visible discrepancies in the resultant display.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to each of U.S. Provisional ApplicationNo. 62/059,121 for “Techniques For Arrayed Printing Of A Permanent LayerWith Improved Speed And Accuracy” filed on behalf of first-namedinventor Michael Baker on Oct. 2, 2014 and U.S. Provisional ApplicationNo. 62/021,584 for “Techniques For Arrayed Printing Of A Permanent LayerWith Improved Speed And Accuracy” filed on behalf of firstnamed-inventor Michael Baker on Jul. 7, 2014. In addition, thisapplication also claims priority to, and is a continuation in-part ofeach of U.S. Utility patent application Ser. No. 14/680,960 for“Techniques for Print Ink Volume Control To Deposit Fluids WithinPrecise Tolerances” filed on behalf of first named inventor Nahid Harjeeon Apr. 7, 2015, U.S. Utility application Ser. No. 14/340,403 for“Techniques for Print Ink Droplet Measurement and Control to DepositFluids within Precise Tolerances” filed on behalf of first-namedinventor Nahid Harjee on Jul. 3, 2014, and U.S. Utility application Ser.No. 14/627,186 for “Encapsulation Of Components Of Electronic DeviceUsing Halftoning To Control Thickness” filed on behalf of first-namedinventor Eliyahu Vronsky on Feb. 20, 2015.

U.S. Utility patent application Ser. No. 14/680,960 is a continuation ofU.S. Utility patent application Ser. No. 14/162,525 (now U.S. Pat. No.9,010,899, issued Apr. 21, 2015). In turn, U.S. Utility patentapplication Ser. No. 14/162,525 claims priority to Taiwan PatentApplication No. 102148330 filed for “Techniques for Print Ink VolumeControl To Deposit Fluids Within Precise Tolerances” on behalf of firstnamed inventor Nahid Harjee on Dec. 26, 2013, and P.C.T. PatentApplication No. PCT/US2013/077720 filed for “Techniques for Print InkVolume Control To Deposit Fluids Within Precise Tolerances” on behalf offirst named inventor Nahid Harjee on Dec. 24, 2013. P.C.T. PatentApplication No. PCT/US2013/077720 claims priority to each of: U.S.Provisional Patent Application No. 61/746,545 for “Smart Mixing” filedon behalf of first named inventor Conor Francis Madigan on Dec. 27,2012; U.S. Provisional Patent Application No. 61/822,855 for “Systemsand Methods Providing Uniform Printing of OLED Panels” filed on behalfof first named inventor Nahid Harjee on May 13, 2013; U.S. ProvisionalPatent Application No. 61/842,351 for “Systems and Methods ProvidingUniform Printing of OLED Panels” filed on behalf of first named inventorNahid Harjee on Jul. 2, 2013; U.S. Provisional Patent Application No.61/857,298 for “Systems and Methods Providing Uniform Printing of OLEDPanels” filed on behalf of first named inventor Nahid Harjee on Jul. 23,2013; U.S. Provisional Patent Application No. 61/898,769 for “Systemsand Methods Providing Uniform Printing of OLED Panels” filed on behalfof first named inventor Nahid Harjee on Nov. 1, 2013; and U.S.Provisional Patent Application No. 61/920,715 for “Techniques for PrintInk Volume Control To Deposit Fluids Within Precise Tolerances” filed onbehalf of first named inventor Nahid Harjee on Dec. 24, 2013.

U.S. Utility patent application Ser. No. 14/340,403 in turn is acontinuation in-part of each of PCT Patent Application No.PCT/US2014/035193 for “Techniques for Print Ink Droplet Measurement andControl to Deposit Fluids within Precise Tolerances,” filed on behalf offirst-named inventor Nahid Harjee on Apr. 23, 2014 and U.S. Utilitypatent application Ser. No. 14/162,525 for “Techniques for Print InkVolume Control To Deposit Fluids Within Precise Tolerances” filed onbehalf of first named inventor Nahid Harjee on Jan. 23, 2014, and alsoclaims benefit to each of U.S. Provisional Patent Application No.61/816,696 for “OLED Printing Systems and Methods Using Laser LightScattering for Measuring Ink Drop Size, Velocity and Trajectory” filedon behalf of first named inventor Alexander Sou-Kang Ko on Apr. 26,2013, U.S. Provisional Patent Application No. 61/866,031 for “OLEDPrinting Systems and Methods Using Laser Light Scattering for MeasuringInk Drop Size, Velocity and Trajectory” filed on behalf of first namedinventor Alexander Sou-Kang Ko on Aug. 14, 2013 and Taiwan PatentApplication 102148330 filed for “Techniques for Print Ink Volume ControlTo Deposit Fluids Within Precise Tolerances” on behalf of first namedinventor Nahid Harjee on Dec. 26, 2013.

PCT Patent Application No. PCT/US2014/035193 in turn claims priority toU.S. Provisional Patent Application No. 61/816,696 for “OLED PrintingSystems and Methods Using Laser Light Scattering for Measuring Ink DropSize, Velocity and Trajectory” filed on behalf of first named inventorAlexander Sou-Kang Ko on Apr. 26, 2013, U.S. Provisional PatentApplication No. 61/866,031 for “OLED Printing Systems and Methods UsingLaser Light Scattering for Measuring Ink Drop Size, Velocity andTrajectory” filed on behalf of first named inventor Alexander Sou-KangKo on Aug. 14, 2013, and U.S. Utility patent application Ser. No.14/162,525 for “Techniques for Print Ink Volume Control To DepositFluids Within Precise Tolerances,” filed on behalf of first namedinventor Nahid Harjee on Jan. 23, 2014.

U.S. Utility patent application Ser. No. 14/627,186 is a continuation ofU.S. Utility application Ser. No. 14/485,005 (now U.S. Pat. No.8,995,022, issued on Mar. 31, 2015). U.S. Utility patent applicationSer. No. 14/485,005 in turn claims priority to U.S. Provisional PatentApplication No. 61/915,149 for “Ink-Based Layer Fabrication UsingHalftoning Variation” filed on behalf of first-named inventor EliyahuVronski on Dec. 12, 2013, U.S. Provisional Patent Application No.61/977,939 for “Ink-Based Layer Fabrication Using Halftoning To ControlThickness” filed on behalf of first-named inventor Eliyahu Vronski onApr. 10, 2014, U.S. Provisional Patent Application No. 62/005,044 for“Ink-Based Layer Fabrication Using Halftoning To Control Thickness”filed on behalf of first-named inventor Eliyahu Vronski on May 30, 2014,and U.S. Provisional Patent Application No. 62/019,076 for “Ink-BasedLayer Fabrication Using Halftoning To Control Thickness” filed on behalfof first-named inventor Eliyahu Vronski on Jun. 30, 2014.

Priority is claimed to each of the aforementioned applications and eachof the aforementioned patent applications is hereby incorporated byreference.

BACKGROUND

Some manufacturing technologies use a printing process to deposit alayer of material on a substrate as part of an assembly process. Forexample, multiple solar panels or organic light emitting diode (OLED)displays can be manufactured together on a common glass or othersubstrate, with multiple panels eventually being cut from the commonsubstrate to create respective devices. The printing process depositsliquid (e.g., similar to an “ink”) having a solvent that suspends orcarries a material from which a respective permanent layer is formed,e.g., by curing, drying or otherwise “processing” the liquid to apermanent form. The liquid is deposited for each product in a mannerthat is carefully controlled, so that each deposited layer alignsclosely in position with underlying layers and desired product positionon the substrate. Such alignment is particularly important where a highdegree manufacturing precision is required, as for example, where theprocess is used to fabricate a dense pattern of microelectronicstructures or optical structures, with each layer of each structurehaving carefully-controlled dimensions (including thickness).

Returning to the OLED display example for purposes of illustration, eachflat panel device being manufactured in parallel on a common substratefeatures individual pixel color components which are typicallyfabricated in fluidic wells that hold light generating elements andelectrodes. Each deposited layer helps determine proper operation of theindividual pixels; the more accurate (and the better aligned andcontrolled) each deposition process, the smaller the pixels can be madeand the more reliable the operation of finished optical or electricalstructure at its particular size dimensions. Variations for a givenpanel (including thickness variations) from pixel-to-pixel areundesired, as these can produce visible defects in the finished product;for example, a typical OLED display (for example, used as an HDTVscreen) can involve many millions of pixels in a compact space, and ifpixels have even slight variations in liquid deposited via the printingprocess, this can potentially be seen as a brightness or colordifference by the human eye. For such manufacturing applications,precise printer control is therefore required, for example, at micron orfiner resolution, and with a maximum variation in aggregate per-areafluid deposition volume of less than one-half-percent.

In addition, to produce products at an acceptable consumer price point,it is desired to maximize manufacturing throughput. If a givenmanufacturing device (e.g., including an industrial printer) takessubstantial time for each layer, this translates to slower manufacture,and to an increased consumer price point; such increased price pointthreatens viability of the manufacturing process.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A shows layout of a substrate that is to receive printing of aliquid that will form permanent layers of respective products, atlocations 107; an overall print area intended for access by nozzles of aprinthead is represented by dashed line box 103.

FIG. 1B shows a print area 125 similar to dashed line box 103 from FIG.1A, but where the substrate is unintentionally offset in position, suchthat without correction, printing would occur in the wrong location, andwould result in misregistration.

FIG. 1C shows a print area 135 similar to dashed line box 103 from FIG.1A, but where there is substrate rotational error.

FIG. 1D shows a print area 147 similar to dashed line box 103 from FIG.1A, but where substrate misalignment represents a scaling error, e.g.,where individual, arrayed products can each have dimensional error (aswell as positional error).

FIG. 1E shows a print area 155 similar to dashed line box 103 from FIG.1A, but where substrate misalignment (e.g., edge distortion in an edgeguided alignment process) results in distortion in two independentdimensions.

FIG. 1F shows a print area 163 similar to dashed line box 103 from FIG.1A, but where different types of errors are represented, each affectingdifferent parts of the substrate.

FIG. 2A provides a flow chart 201 relating to alignment of one or moreprint deposition areas relative to substrate position.

FIG. 2B provides another flow chart 221 related to alignment of one ormore print deposition areas relative to substrate position.

FIG. 2C is a screen shot from a recipe editor and panel definitionsoftware, used to define layer geometries for each product design in anarray (i.e., the array is to be fabricated using a common substrate, andlayer deposition is to be repeated for a series of substrates).

FIG. 3A provides a flow chart 301 relating to one specific method ofadjusting a “template” to fine-tune printing in dependence on detectederror.

FIG. 3B provides another flow chart 351 relating to one specific methodof adjusting a “template” to fine-tune printing in dependence ondetected error.

FIGS. 4A-4I are used to discuss treatment of alignment errors and, morespecifically, to explain processes for assigning or reassigningprinthead nozzle firing decisions, to fine-tune printing.

FIG. 4A shows a layout of a printhead 407 relative to a region 403,where the presence or absence of “Xs” at locations in a “print grid”respectively denote that a droplet will be fired by the printhead in aspecific area (e.g., from nozzle 410 at position 404) or withheld at aspecific area (e.g., from nozzle 410 as it traverses position 405). Forexample, FIG. 4A could be a section of a “bitmap” (i.e., representingintended nozzle firing decisions over a part of a substrate, as theprinthead and the substrate moved relative to each other in a scanningmotion). Note that as used herein, the term “bitmap” refers toper-nozzle data irrespective of whether the data for each nozzleconsists of a single bit or multiple bits; for example, in oneembodiment, 4 bits of data can be used (i.e., representing sixteenpossible values, one of which represents a decision to not fire thenozzle, and others of which represent different preprogrammed nozzledrive waveforms that can be ‘sent’ to the nozzle. Clearly, manyalternatives are possible.

FIG. 4B shows a layout of the original print grid 403 from FIG. 4A, butwhere the substrate is misaligned relative to the intended print areaand where different nozzles can be used to compensate for this alignmenterror without adjusting scan path(s); note that in the depicted example,the misalignment may not “cleanly” align with nozzle spacing or “pitch,”e.g., a greater or fewer number of nozzles, and a different set ofnozzles of the printhead might now overlap desired print region 412 asthe printhead and substrate are moved relative to each other.

FIG. 4C shows a layout 421 where a print grid is seen to be overlaidonto a desired print region 412 from FIG. 4B.

FIG. 4D shows a relative layout 431 of the region 403 from FIG. 4A, butwhere the intended print area or product geometry 433 is seen rotatedrelative to that region, due to substrate error or other misalignment.

FIG. 4E shows a layout 441 where a print grid is seen to be overlaidonto a desired print region 433.

FIG. 4F shows a layout of the original printer grid 403, but where,relative to the specific substrate, there is a detected scaling error,as reflected by desired print region 455.

FIG. 4G shows a layout 461 where a print grid is seen to be overlaidonto the desired print region 455 from FIG. 4F.

FIG. 4H shows a layout of the original print grid from FIG. 4A but wherethere is detected skew error 475, e.g., due to some type of distortionor linear advancement error affecting the substrate, it is actuallydesired to print along the contours of a parallelogram (represented byshape 475).

FIG. 4I shows a layout 481 where the print grid is seen overlaid one toa desired print region 475; with printing corrected using the print gridof FIG. 4I, and using the techniques presented herein, printing can beprecisely aligned (i.e., represented by the shape 475).

FIG. 5A shows circuitry used to assign or adjust nozzle drive waveforms(i.e., electronic drive signals) to/for different nozzles of aprinthead.

FIG. 5B shows per-nozzle drive circuitry that can be used to store datafor a corresponding printhead nozzle, where the stored data enablesprogrammable waveform definition (and, thus, variable volume, droplettrajectory, droplet landing location, velocity, or other per-nozzledroplet parameters).

FIG. 5C shows an exemplary waveform, and is used to help explain howthat waveform can be used to vary nozzle droplet parameters byprogrammable adjustment.

FIG. 5D shows another example of drive circuitry for nozzles of aprinthead.

FIG. 6A is an illustrative view showing a series of optional tiers,products or services that can each independently embody techniquesintroduced herein; for example, the techniques presented herein can beimplemented in the form of software (per numeral 603), or as printercontrol data (per numeral 607, to be used to control a printer to printon a substrate), or as a product made in reliance on these techniques(e.g., as exemplified by numeral 613, 615 or 617).

FIG. 6B provides a schematic view of a fabrication apparatus thatincludes a printer.

FIG. 6C shows a plan view of a print area within a fabricationapparatus; this print area can optionally be contained within a gasenclosure, i.e., such that printing occurs in a controlled atmosphere.

FIG. 6D provides a functional block diagram of a fabrication apparatusthat includes a printer.

FIG. 7 provides a flow chart 701 used to describe measurement of effectsof individual nozzle variations and/or nozzle-drive waveform variations,and related compensation techniques. In one embodiment, not only isprinting adjusted for positional error but, in addition,nozzle-to-nozzle variations are taken into account in the adjustment, soas to permit printing to occur within carefully defined tolerances.

FIG. 8A is an illustrative diagram that shows a droplet measurementsystem capable of measuring droplet volumes for each nozzle of a largeprinthead assembly. For example, such a system can be used to measurethe nozzle-to-nozzle variations just referenced.

FIG. 8B is a method diagram that shows various processes and optionsassociated with measurement of droplet particulars for each nozzle, toachieve a high-confidence understanding of expected dropletcharacteristics.

FIG. 8C shows a flow diagram associated with an embodiment of dropletmeasurement.

FIG. 8D shows a flow diagram associated with nozzle validation; that is,in one embodiment, measurement can be used to qualify or disqualifynozzles (in addition to the other purposes described herein).

FIG. 9A provides a block diagram associated with a raster process; morespecifically, FIG. 9A helps explain how the results of dropletmeasurement can be integrated with detected substrate errors (e.g.,position, rotation, scaling or skew error) in order to provide precisionprinting. A shaded area (907) represents a single scan path, while aclear area (908) represents another.

FIG. 9B shows a flow diagram associated with printing on a substrate aspart of a manufacturing process.

FIG. 9C shows another flow diagram associated with printing on asubstrate as part of a manufacturing process.

FIG. 10A shows a flowchart associated with printing on a substrate aspart of a manufacturing process.

FIG. 10B provides another flowchart associated with printing on asubstrate as part of a manufacturing process.

FIG. 10C provides a flowchart 1041 relating to antialiasing forgeographies that are to receive printing, e.g., to test whether“adjusted” printer control data still meets one or more desired criteria(e.g., th₁≦volume≦th₂), and to further adjust printer control data if itdoes not meet the one or more desired criteria.

FIG. 10D provides a flowchart 1061 relating to incorporating updatednozzle-droplet data into the rendering of printer control data tomitigate substrate-printer variation.

FIG. 10E provides yet another flowchart 1081 relating to incorporatingupdated nozzle-droplet data into the rendering of printer control datato mitigate substrate-printer variation.

FIG. 11A is a block diagram showing a parallel processing environment.

FIG. 11B is a block diagram showing how rendering and/or rasterizationof a print image is performed in a parallel processing environment.

The subject matter defined by the enumerated claims may be betterunderstood by referring to the following detailed description, whichshould be read in conjunction with the accompanying drawings. Thisdescription of one or more particular embodiments, set out below toenable one to build and use various implementations of the technologyset forth by the claims, is not intended to limit the enumerated claims,but to exemplify their application. Without limiting the foregoing, thisdisclosure provides several different examples of techniques used tofabricate a thin film for each of multiple products of a substrate (orother array of products) as part of an integral, repeatable printprocess. The various techniques can be embodied as software forperforming these techniques, in the form of a computer, printer or otherdevice running such software, in the form of control data (e.g., a printimage) for forming such a film layer, as a deposition mechanism, or inthe form of an electronic or other device fabricated as a result ofthese techniques (e.g., having one or more layers produced according tothe described techniques). While specific examples are presented, theprinciples described herein may also be applied to other methods,devices and systems as well.

DETAILED DESCRIPTION

This disclosure provides techniques, processes, apparatuses, devices andsystems that can be used to more quickly and more reliably fabricateproducts via a printing process, and products made according to such aprocess.

An assembly line process uses a printer to print (i.e., deposit)droplets of liquid onto each substrate in a series of substrates. Theliquid is then cured, dried, or otherwise processed to form a permanentlayer of material (i.e., a permanent thin film). Each substrate is usedto fabricate one or more products, and the layer will typically beformed for each product carried by the substrate. Once printing iscompleted, the substrate is advanced and a new substrate is loaded, andthe process is repeated. Processing, e.g., to cure the liquid, in someembodiments can happen in situ or in another position in the assemblyline, and typically the printing and processing is performed within acontrolled atmosphere to minimize particulate, oxygen or moisturecontamination. In specifically contemplated applications, the printer isused to deposit a single layer of an organic light emitting diode(“OLED”) display panel or a solar panel. For example, in the fabricationof a high-definition OLED television screen, such a process can be usedto deposit one or more light generating layers for each pixel of adisplay (i.e., each discrete light generating element). Although thedescribed techniques can be applied to many types of materials, and tomany types of products other than flat panel displays, the use of aprinter and associated processing has been found especially useful todeposit layers of organic materials that cannot easily be depositedusing other processes, and many examples presented herein will thereforefocus on these materials. As with other types of products andmanufacturing processes, alignment in printing and layer thickness muchbe achieved with a high degree of accuracy to facilitate small, reliableelectronic components (e.g., micron scale), with low variation and highmanufacturing throughput.

Because of various process corners associated with different substrates,the assembly line equipment, human handling and a myriad of otherfactors, each substrate may vary slightly in position, rotation, scale,skew or other dimensions as the substrate is moved into and through theprinter. Some forms of error might be unique to the substrate (e.g.,warping of a substrate or edge nonlinearity), while other forms of errormight represent repeating system errors (e.g., a substrate isincorrectly edge-guided through the printer with repeatable motion errorcaused by the system itself). Whatever the source, as the printingprocess is intended to print identical products on each substrate in theseries, it is generally desired to detect and mitigate positional error.

Thus, in one embodiment, a detection mechanism is used to detectfiducials on each substrate when in proximity to the printer. Thefiducials are used to identify product position notwithstandingsubstrate-to-substrate error or other deviation from expected productposition, orientation and/or dimensions. The detected product positionis compared to expected position and used to identify that error, so asto (in-software) transform or adjust printer control data (i.e., tomodify either that data or how it is rendered to perform printing), toprecisely register the to-be-printed-layer with any underlying productdimensions. As used herein, “position” or “product position” shouldgenerally be understood to include any of skew, scale, orientation,etc., even though these things are not individually listed beyondmention of “position.”

Note that in a conventional printing process, an assemblage comprisingone or more printheads, each with nozzles, is transported relative tothe substrate being printed upon, in one or more raster sweeps. Eachsweep defines an “in-scan” dimension of the substrate and, after eachsweep, the printhead and/or the substrate are repositioned in a“cross-scan” dimension of the substrate, in preparation for an ensuingsweep. Each printhead can have hundreds to thousands of nozzles, each ofwhich is to jet a droplet of liquid, where the liquid is analogous to anink and includes a material that will be cured or otherwise processed toform the desired permanent layer. For example, with one knowntechnology, the liquid is a monomer or polymer, and an ultraviolet cureprocess is used following printing to process the deposited liquid toform a permanent layer.

In more detailed variations of this first embodiment, a number ofmechanisms can be used to reconcile goals of fast printing, accurateprinting and precise layer thickness and registration.

In a first implementation, with error identified (e.g., a linear ornonlinear shift in position, rotational, skew or scaling), new nozzlefiring decisions can be generated in a manner dependent on detecteddeviation from ideal position and in a manner that does not requireshift or alteration in preplanned raster sweeps between the printheadassembly and the substrate. That is, since printing time (and thusmanufacturing throughput) is directly related to the number of rastersweeps required to cover all regions of the substrate that are toreceive liquid, this number of raster sweeps and their respectivepositions in one embodiment are not changed, but rather, potentially newnozzles and/or drive parameters are individually assigned in a mannerthat permits printing to occur to deposit the intended density andpattern of droplets from the printhead assembly, but in a manner wherenozzle assignments and/or drive parameters (e.g., drive waveforms) aretransformed or rendered relative to the original printer control data soas to exactly register with any underlying product layers or otherwisealign exactly with intended product geometry. Note that this manner ofprocessing is optional, i.e., in another contemplated embodiment, rastersweeps are reassessed to potentially employ different offsets of theprinthead assembly relative to the substrate (e.g., differentadvancement patterns in the cross-scan direction and/or different numberof scans or sweeps).

Depending on environment, simply “shifting” nozzle firing decisionsmight not always produce the desired deposition parameters. For example,in one contemplated environment in which printing is used to depositlight generating elements in fluidic “wells” that contain depositedliquid until that liquid is cured, error might not cleanly align withnozzle spacing or nozzle firing timing, such that a linear shift innozzle firing assignments might position too great or too few a numberof deposited droplets in a pixel well. To address this, in oneembodiment, an “antialiasing” process is used, pursuant to which one ormore processors acting under the control of instructional logic testexpected position of each pixel well (given detected error) againstexpected liquid volume and, should expected aggregate volume stray bymore than a threshold amount from an ideal value or range ofacceptability, selectively revisit “shifted” nozzle assignments andadjusts one or more of number of nozzles that will fire droplets intothe pixel well. This then helps ensure that precisely the intendedamount of liquid is deposited in intended locations.

In another embodiment, droplets produced by each nozzle are empiricallymeasured in situ, and measured droplet characteristics that vary fromnozzle-to-nozzle, or that depend on drive parameters used to ejectdroplets from a nozzle, are stored and factored into nozzle assignment.For example, in a first variation, individual nozzles can bequalified/disqualified dependent on whether associatedempirically-measured droplet parameters for the nozzle (and for applieddrive parameters) meet criteria for acceptable droplet production. Thus,if positional error and associated registration imply an un-validatednozzle should not be used for deposition, instructional logic can usevalidation data to assign nozzles so as to instead use other nozzles ordifferent droplet ejection parameters (e.g., a different drive waveformto control a selected nozzle). In a second variation, each given nozzle(and each one of plural, alternative drive waveforms that can be used todrive the given nozzle) is measured as to expected droplet volume,trajectory and/or droplet landing position, and this data is thenfactored into error processing or initial nozzle assignment. To cite asimple example, if two adjacent nozzles are to be relied on torespectively deposit 9.97 and 10.03 picoliter (pL) droplets into afluidic well for a total volume of 20.00 pL of liquid, and substrateerror implies that two other nozzles will be used to perform thedeposition, (a) non-adjacent nozzles expected to produce 9.90 and 10.10pL droplets can be assigned to perform the deposition (preserving theexpectation of 20.00 pL aggregate volume), and/or (b) nozzle driveparticulars (e.g., drive waveform) for one or more nozzles can beadjusted to produce droplets having adjusted volume or trajectorycharacteristics from pre-selected nozzles, so as to maintain expectedaggregate volume in the fluidic well notwithstanding detected error.These types of processing also are optional and are not required for allembodiments.

Note that the printer control data can take many forms depending onembodiment. In one implementation, “recipe” information describingdesired dimensions (e.g., including thickness) for the desired layer foreach product can be stored as a cached template and then rendered in anadjustable manner that accommodates run-time error. In a secondimplementation, this recipe information can be partially pre-processedand stored in an object (vector) or other representation in advance,also as a cached template for use in processing each substrate; aspositional or alignment error is detected for each new substrate, thetemplate is retrieved and modified as appropriate in rendering the finalprinter control data (that is, the nozzle firing decisions, rastersweeps, and related timing, as appropriate). To cite another example, inanother implementation, recipe data is received for a product (and/orarray) and is rendered into a bitmap representing printing decisions;the bitmap is essentially an array of nozzle firing decisions orequivalent data at each node of a print grid that represent triggersthat will cause the nozzle to fire or not fire a droplet at a discreteposition on the substrate during a scanning motion of the printheadrelative to the substrate. This information can also include variableper-nozzle drive waveform definition or selection. The bitmap is cachedas a template and, at run time, is retrieved, modified to distortprinting to match error via direct processing on the bitmap, and is thenused to control printing. Naturally, other examples exist, i.e., witheach variation, detected error is factored in some manner into therendering process so as to customize printing in view of the detectederror, so as to achieved registration of layers.

With each embodiment, to facilitate highly accurate printing withoutincreasing printing time, detected misalignment of the substrate (or anyindividual product represented thereon) in any given manufacturingiteration can be corrected at least partially in software, in real time.This correction then reduces the need for time-consuming very highprecision mechanical alignment or repositioning, as well as the need fora very high precision alignment mechanism. This lowers cost andincreases manufacturing throughput without sacrificing accuracy andreliability. In one specifically contemplated application related toarrayed printing of multiple large-scale OLED TV screens, a single largesubstrate might include 6-8 HDTV screens (e.g., panels or subpanels,which will be used interchangeably); it is presently contemplated for asuccessful manufacturing process that a layer to be printed on thesubstrate should take no more than 90 seconds per substrate. In someembodiments, this maximum printing time is expected to be 45 seconds orless. As each screen or panel involves millions of pixels, alignmentshould be precise for the manufacture of high quality displays; it istherefore desired to print liquid onto the substrate using a processthat takes less than a few seconds (e.g., 2 seconds) to detect andcorrect substrate and/or product misalignment or other errors. Thedisclosed embodiments facilitate this speed in manufacturing (andmanufacturing throughput) and help produce smaller, precisionregistration products.

Many manufacturing applications are relatively robust to roughmechanical alignment of products in-assembly. For the disclosedembodiments, the fine-precision alignment performed by one or moreprocessors (i.e., machines) acting under the control of software(instructions or instructional logic stored on non-transitorymachine-readable media) typically adjusts for millimeter tosub-millimeter error (e.g., from nanoscale to hundreds of microns, orless) in positional offset, rotational offset, skew, scaling error, orfor other distortions. Note that for some applications which featurevery dense precision structures (e.g., HDTV applications having millionsof pixels), and/or where thousands or printhead nozzles are involved,error processing can require substantial computing resources. As notedabove, in one embodiment, it is desired to perform error compensationusing hardware logic and/or software logic in seconds, e.g., 2 secondsor less. To facilitate this end, certain embodiments below presenthardware designs that rely on parallel processing (e.g., multipleprocessors or a multicore processing) and techniques for process threadassignment that permit this computation to occur quickly. For example,to foreshadow an embodiment that will be further discussed below, asupervisory processor or group of processors can detect error anddetermine a formulation for rendering or transforming original recipeinformation (or other cached, template data). The formulation can belinear over the substrate, or can vary locally (e.g., be non-linear ordiscontinuous). The supervisory processor then assigns geographicalsegments and an associated affine transform to each core of a multicoreprocessor for processing. In one design, each core has its own dedicatedmemory for data processing and manipulation; the supervisory processoridentifies the geographic segment to be modified by each core and theassociated modification algorithm (e.g., affine transform), and providesthis information to the respective cores, and multiple cores then eachperform their allocated tasks to contribute to finishing a transformedoutput that represents adjusted printer control data for the substrateas a whole; this transformed output is suitable for use in immediateprinting. If desired, the memory used for manipulation can also bedesigned to provide direct memory access (DMA) to speed manipulation ofcached template data and its adaptation to and use in printing. Forembodiments which use dozens to hundreds of cores, or more, thissubstantially reduces processing time needed to re-render the desiredprint job. Other designs are also possible; for example, instead ofassigning different geographies to each core, different mathematicaloperations (or different, sequential processes) can be assigned to eachcore. As this example should make clear, nearly any partition offunctions or processing can be provided for to maximize efficiency orotherwise reduce processing time. A parallel processing environment suchas just discussed should also be viewed as optional relative to othertechniques described herein.

The present disclosure provides a number of hardware (i.e., circuit orcircuitry) implementations that facilitate highly accurate printing inan assembly line-style process, and software techniques that can be usedin lieu of or in addition to such hardware. Generally speaking, featuresdiscussed below can be mixed and matched (or are otherwise optional) andcan vary according to implementation. For example, one embodimentdiscussed below provides hardware that can be used to pre-store a number(e.g., 16) of customizable nozzle drive waveforms for each of manynozzles (e.g., hundreds to tens of thousands of nozzles) used by aprinter. Each waveform is selected in advance to produce a slightlydifferent expected droplet parameter (e.g., volume, trajectory, and soforth), providing a range of possible droplets producible from thatnozzle; the system selects these waveforms in advance so as to provide arange of choices, and programs the various waveform choices in advanceto drive circuitry for each nozzle. Then, at run time, the system simplyselects one of the waveforms. In one embodiment, there are sixteen suchselections (e.g., one “zero” waveform, representing a non-firingdecision, and fifteen variable drive waveforms). In another embodiment,a default waveform can be programmed asynchronously (i.e., in advance),and a binary “trigger” then applied to “launch” whichever waveform hasmost recently been programmed as a default. Once again, these variousfeatures are optional and are not required for all embodiments, andvarious disclosed features may be used in any desired combination orpermutation as suited to the implementation. All such combinations andpermutations and any such combinations and permutations are contemplatedby the teachings of this disclosure.

Specifically contemplated implementations can include an apparatuscomprising instructions stored on non-transitory machine-readable media.Such instructional logic can be written or designed in a manner that hascertain structure (architectural features) such that, when theinstructions are ultimately executed, they cause the one or more generalpurpose machines (e.g., a processor, computer or other machine) tobehave as a special purpose machine, having structure that necessarilyperforms described tasks on input operands in dependence on theinstructions to take specific actions or otherwise produce specificoutputs. “Non-transitory machine-readable media” as used herein meansany tangible (i.e., physical) storage medium, irrespective of how dataon that medium is stored, including without limitation, random accessmemory, hard disk memory, optical memory, a floppy disk or CD, serverstorage, volatile memory and other tangible mechanisms whereinstructions may subsequently be retrieved by a machine. Themachine-readable media can be in standalone form (e.g., a program diskor solid state device) or embodied as part of a larger mechanism, forexample, a laptop computer, portable device, server, network, printer,or other set of one or more devices. The instructions can be implementedin different formats, for example, as metadata that when called iseffective to invoke a certain action, as Java code or scripting, as codewritten in a specific programming language (e.g., as C++ code), as aprocessor-specific instruction set, or in some other form; theinstructions can also be executed by the same processor or differentprocessors or processor cores, depending on embodiment. Throughout thisdisclosure, various processes will be described, any of which cangenerally be implemented as instructions stored on non-transitorymachine-readable media, and any of which can be used to fabricateproducts using for example a microelectronics, micro-optics, “3Dprinting” or other printing process. Depending on product design, suchproducts can be fabricated to be in saleable form, or as a preparatorystep for other printing, curing, manufacturing or other processingsteps, that will ultimately create finished products for sale,distribution, exportation or importation. Also depending onimplementation, the instructions can be executed by a single computerand, in other cases, can be stored and/or executed on a distributedbasis, e.g., using one or more servers, web clients, orapplication-specific devices. Each function mentioned in reference tothe various FIGS. herein can be implemented as part of a combinedprogram or as a standalone module, either stored together on a singlemedia expression (e.g., single floppy disk) or on multiple, separatestorage devices. The same is also true for the print image or printercontrol data generated according to the processes described herein,i.e., recipe information, a template or the result of processing suchrecipe information or template can be stored on non-transitorymachine-readable media for temporary or permanent use, either on thesame machine or for use on one or more other machines; for example,printer control data can be generated using a first machine, and thenstored for transfer to a printer or manufacturing device, e.g., fordownload via the internet (or another network) or for manual transport(e.g., via a transport media such as a DVD) for use on another machine.

Also, reference has been made above to a detection mechanism and tofiducials that are recognized on each substrate. In many embodiments,the detection mechanism is an optical detection mechanism that uses asensor array (e.g., a camera) to detect recognizable shapes or patternson a substrate. Other embodiments are not predicated on an array, forexample, a line sensor can be used to sense fiducials as a substrate isloaded into or advanced within the printer. Note that some embodimentsrely on dedicated patterns (e.g., special alignment marks) while othersrely on recognizable substrate features (including geometry of anypreviously deposited layers), each of these being a “fiducial.” Inaddition to using visible light, other embodiments can rely onultraviolet or other nonvisible light, magnetic, radio frequency orother forms of detection of substrate particulars relative to expectedprinting position.

Having thus introduced some basic embodiments, this disclosure will nowproceed to discuss more detailed implementations. FIGS. 1A-1F are usedto illustrate various principles associated with printer control dataadjustment in a repeatable manufacturing process.

FIG. 1A illustrates layout of a hypothetical substrate 101. Morespecifically, the substrate includes a number of alignment marks 105, aprint area 103 defined relative to the alignment marks, and areas 107corresponding to a number of products that are to be formed or thatalready have base layers deposited as part of the process of productformation. For purposes of illustration, it may be assumed the substrate101 will be used to form many products 107, and each “panel” that willbe cut from the substrate to form an independent solar panel or displaydevice, but the invention is not so limited. In one embodiment, eachpanel 107 will be an independent OLED panel, and the substrate 101 is alarge sheet of glass.

It is desired to employ a printer to jet liquid onto the array orsubstrate 101 in an integral printing process, notwithstanding thepresence of multiple products; the liquid carries a material such that,following deposition of the liquid and its cure or other processing, thematerial and/or liquid will become a permanent part of each resultantproduct, and such that the layer will have a specifically plannedthickness. In an optional embodiment, layer thickness is imparted usingcontrolled droplet deposition where the volume or density of depositedliquid per unit area is used to build layer thickness. That is, theliquid has limited spreading that produces blanket liquid coveragewithout undesired holes or gaps, or the liquid is otherwise deposited orhardened in a manner that will be geometrically confined, all in amanner that will otherwise result in the specifically planned thickness;this process is generally referred to herein as “halftoning,” eventhough deposited fluid is typically colorless and is not being used tocreate any type of tone (i.e., “half,” “blended” or otherwise). Notethat in a typical implementation, the printer prints the entiresubstrate (i.e., a layer of each product in the array), and thesubstrate is then transported from the printer to a separate curechamber where the liquid will be cured or otherwise hardened, all in thepresence of a controlled atmosphere (e.g., a nitrogen or othernon-ambient-air atmosphere, which prevents the liquid from being exposedto moisture, oxygen or other forms of unwanted particulate). It will beassumed for this example that recipe data is produced in advance whichcalls upon the printer to deposit the desired material at discretelocations within the confines of the overall print area 103. Simplystated, the recipe data for each product describes layer thickness anddimensions for that product, and any desired particulars such as cornerrounding or edge buildup profiles, and the recipe data for the arraydescribes where each product's layer (i.e., the product recipe data) isto be positioned relative to the substrate. The recipe data, asprocessed or rendered, will instruct an ink jet printer to depositliquid into each individual product area 107 on a reproducible basisthat will be repeated for many ensuing, similar substrates. The recipedata (or any processed version thereof) is stored or “cached” in memoryfor use as a template that will be used to cause the printer to depositthe liquid on each substrate in the series of substrates. FIG. 1A showsa single one of these substrates (with many products or “panels”thereon), representing an idealized deposition relative to thesubstrate.

As noted earlier, unfortunately, in practice each array or substrate canhave non-uniformities either in its structure or its position, rotation,scale, skew, or other alignment issues which affect registration of thedeposited layer for one or more of the products; for many manufacturingprocesses, such distortion can be tolerable, but for applications suchas microelectronics, or where very precise alignment is otherwisenecessary, such alignment issues can limit feature size, create productdefects, or otherwise increase time and/or cost of manufacture. It isdesired to avoid and/or compensate for these issues and to provide forprinting that is automatic and is as fast as possible while maintainingaccuracy.

To this effect, in one embodiment, hardware logic and/or instructionallogic adjusts nozzle firing data in view of detected error, in a mannerthat ideally does not require adjusting planned scan paths of theprinter (e.g., only the nozzle data is adjusted); this is not requiredfor all embodiments. The fiducials (e.g., alignment marks oroptically-recognized features of the substrate) are optically-detectedas each new substrate is loaded, advanced or positioned in the printer.Associated, imaged data is then used by a processor to compare actualposition of the substrate (and its panels) to expected position;dependent on deviation, the print image is adjusted so that printingregisters with panel-layout information (and any previously-depositedlayers). The alignment correction performed using these techniques istypically micron scale or finer (e.g., correcting for positional errorsthat are sub-millimeter and, in some embodiments, for positional errorsof 100 microns or even substantially less).

FIG. 1B shows a situation where a substrate is indeed misalignedrelative to the ink jet printer; in this case, whether due to edgeerror, mechanical positioning error, substrate process corners or otherissues, this misalignment creates the potential for alignment errorsbetween layers of each product being fabricated. Note that the depictederror is exaggerated in scale for ease of illustration. Morespecifically, an xy Cartesian error (represented by numeral 123) if leftuncorrected, would result in individual product layers (107) beingoffset relative to the ideal print area 125 on the substrate; thisoffset could cause issues relative to any underlying (orsubsequently-deposited or fabricated) product layers. The techniquesdisclosed herein are used to adjust printer control data so that the inkdeposition is shifted in a manner conforming to the registration error,e.g., the print process is offset (or otherwise transformed) in a mannermatching error in substrate and/or panel position. This detected erroris corrected by generating or adjusting printer nozzle control data in amanner matching such error. As noted earlier, if recipe data ispreprocessed, optional techniques can be used to reassign any priornozzle firing patterns in a manner dependent on the error. Note that inone embodiment, this reassignment typically involves more than simplyshifting all nozzle firing decisions by a vector amount, i.e., topreserve precise liquid fills for the desired area, nozzle firingdecisions can be reassessed in view of nozzle-to-nozzle variations andpositional mismatch with the deposition area of interest (e.g., a pixelwell) and the print grid, and to adjust for other factors (e.g.,antialiasing, as further discussed below). In one embodiment, thisreassignment is performed by a process that operates at the bitmap orvector representation level, effectively transforming individual nozzlefiring decisions dependent on print grid points associated with anypreviously processed or rendered data (e.g., dependent on a templatebitmap), and/or nozzle drive parameters. The use of other adjustmenttechniques such as scan path variation (e.g., adjusting printheadoffsets and rasterization changes) is also possible.

FIG. 1C represents a situation where a substrate bears another form oferror, represented by rotational angle α (numeral 133). If leftuncorrected, this error would result in individual product layers (107)being potentially misaligned with other product layers (e.g., relativeto a desired print area 135 of the substrate). Using techniquesdiscussed herein, this error can be corrected by detecting themisalignment and factoring in rotational adjustment in the rendering ofprinter data, e.g., in hardware, software, or a combination thereof.Once again, if a template print image such as a bitmap has already beengenerated, this correction can optionally be performed directly on acopy of that image, by computing new nozzle firing assignments and/ordrive parameters directly from the preprocessed bitmap (e.g., withouthaving to generate a print image anew from recipe data). As with theprevious example, adjustment results in a per-substrate print processwhere the deposited layer exactly aligns with intended product geometrynotwithstanding error; the printing can be performed almost immediately.

Note that whether error is factored into preprocessed data (such as atemplate or bitmap) or applied directly to originally render printerdata from recipe information is an implementation decision. For an OLEDdevice having millions of pixels (and many millions of potential dropletdeposition points per substrate), per-substrate adaptation of apreviously rendered bitmap can be computationally-prohibitive, dependingon supporting hardware capabilities; in some embodiments, it might befaster to directly render printer data from recipe data in a manner thatfactors detected registration error, and in other embodiments, use of abitmap (or other preprocessing) might be more efficient. For embodimentswhich further use the parallel processing features provided below, agreater number of processing options are available.

FIG. 1D represents yet another type of error that is depicted to belinear across for the entire substrate or product array, in this case,representing a scaling issue. It should be assumed for purposes of thisexample that a substrate is slightly larger or smaller than intended;for example, it could be that due to temperature changes, the substratehas contracted or expanded slightly, in a manner such that error is atleast locally uniform or linear. Thus, to provide a simplified example,it is assumed for this hypothetical that all dimensions and positions ofthe template image should be adjusted by k₁X, k₂Y, where k₁ and k₂ arescalars, and where X and Y represent Cartesian coordinates on thesubstrate. Note that a situation where scaling error is in one dimensiononly (e.g., the X dimension) presents a simplified case where k₂=1). Ifleft uncorrected, scaling error would result in offset error as well asindividual product layers (107) being slightly smaller (149) than thedesired footprint (148) for each panel; similarly, the overall printarea is seen to be slightly smaller (145) than the desired print area(147) for the substrate. To correct for this error, scaling is correctedaccording to k₁ and k₂. Once again, in one embodiment, this can beimplemented by factoring in variables k₁ and k₂ to generate transformedprinter control data (e.g., with potentially different nozzle firingdecisions and mappings, either directly from recipe data or frompreprocessed template data). Antialiasing (as will be discussed below)and/or nozzle droplet particulars can also optionally beapplied/factored as part of this transformation to ensure local densityof deposited liquid in a given location or unit area (i.e., which willgovern thickness) corresponds to the intended layer dimensions. As withthe previous examples, adjustment results in a per-substrate printprocess where the deposited layer exactly aligns with intended productgeometries notwithstanding substrate positional error and where desireddeposition fills, densities and volumes are correct; note that theparticular adjustment relative to FIG. 1D may result in substantialchanges to per-printhead-scan nozzle assignments and, depending onembodiment, can potentially affect the number of scans (depending onembodiment and the nature of the error). That is, in one embodiment asreferenced earlier, nozzle firing decisions are reassigned in dependenton techniques disclosed herein (e.g., without changing position ornumber of scans); in another embodiment, scan paths can be re-optimizedgiven per nozzle-droplet data and error, and different scan paths and agreater or fewer number of scans can be used. Irrespective ofembodiment, printing can be performed almost immediately as planned,with the substrate error being corrected in software, hardware or bothby dynamic adjustments which independently account for positional errorfor each substrate (or a portion of a given substrate on a localizedbasis).

Note once again that all errors depicted in these FIGS. are visuallyexaggerated for purposes of illustration, i.e., if it is assumed that anarrayed area (e.g., glass substrate) is of a scale that is meters wideby meters long, rough mechanical alignment is typically precise tomillimeter scale or better. Thus, in many embodiments, the disclosedtechniques are used to correct for relatively small misalignments (e.g.,tens-to-hundreds of microns or even less).

FIG. 1E represents yet another type of error, e.g., where the individualproduct areas or the substrate as a whole experience skew. Here, theerror is seen to result in Y position error (horizontal directionrelative to the drawing page) that varies depending on X position on thesubstrate (vertical direction relative to the drawing page); as anexample, this type of error might be caused by a substrate edge error orby a transport error that uniquely affects the specific printer ormanufacturing device. In the FIG., all dimensions and positions are seento be skewed by X′=X, Y′=fn{X}, where X′ and Y′ are adjustedcoordinates, as represented by graphic 153. Once again, note that a skewsituation would in practice also result in positional offset errors foreach panel 107 which are in addition to panel skew errors (this is seenin the FIG. as a horizontal offset in panels in one row relative to thenext row). If left uncorrected, skew error would result in individualproduct layers (107) being malformed relative to the desired footprint.To correct for this error, the print image is once againadjusted/transformed in software, to advance-skew panel printing so asto match the underlying error. As with the previous examples, theperformed transformation can include more than simply shifting nozzlefiring decisions and, for example, can feature additional processes toensure deposition of the proper volume of ink in the proper targetregions; this can optionally result in substantial changes toper-printhead-scan nozzle assignments, and potentially affect the numberof scans, as previously discussed. The printing is once again performedalmost immediately, with the substrate error being corrected in softwareby real time adjustment to the template print image or in the renderingof recipe information for the specific substrate.

FIG. 1F represents a hypothetical case where the mentioned errors canaffect each panel independently from one another, and where such errorcan be in addition to, or in lieu of, errors in substrate position. Forexample, FIG. 1F depicts a case where, relative to desired printing area163, a first panel 107′ is seen to be askew, whereas second, third andfourth panels (107″, 107′″ and 107″″) are seen to each respectively haverotational, offset, and scaling errors relative to other panels 107;note that because scaling error for panel 107″″ affects only this panel,positional offset is diagrammatically depicted as small-to-nonexistent.Applying teachings introduced herein, errors for each panel areseparately corrected for by adjusting the rendering that will be used toprint the given array or substrate. In this regard, error for any givenpanel or portion thereof can be complex, with correction modeled as asuperposition or combination of transformation techniques for one ormore of positional offset, rotation, skew and scaling error; this can bedone on an independent basis for a group of panels, a single panel, aspace spanning parts of multiple panels or a part of any given panel.For embodiments that cache a previously-rendered template print image,for each new substrate (e.g., every 45 seconds), a copy of that cachedimage can be manipulated to reduce alignment, orientation or othererrors, reassigning nozzle firing decisions as necessary, without havingto mechanically reposition the specific substrate; for each ensuingsubstrate, e.g., every 45 seconds, an instance of cached templateprinter control data can be once again loaded and used to correct forerror in positioning or alignment specific to the new substrate,producing rendered data that can be immediately applied to printing.

There are a number of techniques for fine-alignment of printer controldata to match substrate or panel deviation from expected positions.First, one contemplated embodiment overlays a print grid onto the actual(i.e., detected) substrate and/or panel position; as previously noted,the print grid can feature “horizontally-separated” nodes representingnozzle pitch on the printhead and “vertically-separated” nodesrepresenting digital timing at which nozzles can be fired, e.g., “everymicron” of distance as the printhead and substrate are “scanned”relative to one another. For each node in this overlaid space, thesystem (i.e., instructional logic running on one or more processors)determines whether a respective nozzle ought to be fired at that pointto deposit a droplet of liquid. For the overlaid space, the firingdecision at each node is a function of original “recipe” data for anideal substrate as well as deviation in position of that node from anequivalent point in a perfectly aligned substrate. In one implementationwhere printer control data is “pre-rendered” to form a bitmap (i.e.,with nozzle firing decisions already assigned in a manner assuminguniform alignment), each firing decision of a print grid overlaid withthe deviated substrate or panel position can be mapped, via atransformation, to an equivalent point in the original bitmap. Toprovide an example, if a given substrate was offset by 31.0 microns “tothe right” of where it should be, firing decisions for each node in theprint grid could be calculated by first identifying the same nodeposition in the original bitmap, then identifying a point 31.0 microns“to the left” of that position and, finally, identifying the firingparticulars associated with the node nearest to that shifted point. Aswill be further discussed below, in such an embodiment, particularlywhere liquid is to be printed in pixel wells, such a process mightresult in too many or two few droplets of the liquid being depositedwithin well confines, and adjustment processes such as antialiasing(discussed below) can be employed to mitigate this possibility. In asecond implementation, each firing decision in the overlaid grid can bea weighted function of firing decisions from a pre-rendered template(e.g., a weighted average of the firing decisions for the four closestprint nodes to a point 31.0 offset microns “to the left” in the originalbitmap. Naturally, many variations and possible adjustment mechanismswill occur to those having ordinary skill in the art. Other embodimentscan employ imported alignment data or in situ measurement of nozzleparameters, which are then factored into the rendering of printercontrol data for the given substrate, antialiasing, droplet density(halftone pattern) adjustment and other processes, as appropriate; eachof these helps produce a more reliable deposition by using an additionalprocess or processes to ensure that the proper amount and/or density ofliquid is printed in discrete regions of the substrate. In someembodiments, the number of scan paths or printhead cross-scan offsetscan be revisited, to optimize printing time. The various combinations ofdisclosed techniques and their relative benefits will be apparent tothose skilled in the art in view of the discussion below.

FIG. 2A is used to introduce some exemplary processing tasks. Morespecifically, FIG. 2A shows a flow chart 201 with certain functionsdelineated as performed as part of an offline process (i.e., abovedashed line 209) or as performed during runtime (i.e., online as part ofthe manufacturing process, below dashed line 209). A computer (e.g.,standalone or part of a manufacturing device such as an industrial ormanufacturing printer) first receives information describing desireddeposition of a layer across the substrate, per numeral 203. As noted atthe right side of FIG. 2A, a number of variations are contemplated. Forexample, one embodiment (204) contemplates manufacturing of manyproducts at once, as part of an arrayed deposition. Returning briefly toFIG. 1A, it could be for a particular manufacturing process that layersrespective to each of the illustrated 15 panels are to be exactly thesame as one another in width, length and thickness; for example, asingle recipe (representing one of these panels) could be electronicallyloaded and arrayed by hardware logic or instructional logic, or both, togenerate an aggregate print image with aggregate print data for theexpected printing locations for 15 individual products. This need not bethe case for all embodiments. For example, TV screens of a first sizecould be presented by the first horizontal row of panels, and TV screensof a second size could be presented by a second row of panels, bothtogether on the same substrate; each panel would have differentmanufacturing particulars in this example. Whether or not multipleproducts are represented by each substrate, the method can includereceiving information such as desired position of each layer (e.g.,“top-left” corner position and length and width dimensions, per numeral205, and desired layer thickness(es), per numeral 206). In one example,“recipe editor” software can be used to define layer parameters for asubstrate carrying one or more products, (e.g., see the discussion ofFIG. 2C, below). The computer then stores information representing thedesired layer for use as a template in processing many substrates, i.e.,each in a sequence run as part of an assembly line process. The storedinformation is optionally pre-rendered as a bitmap or other form torepresent printing of an “idealized” substrate (i.e., one that ispositioned perfectly, with all products thereon positioned perfectly),or is somehow otherwise associated with a default substrate/productposition.

During runtime, as each new substrate is loaded into the printer orotherwise received, the substrate is roughly positioned using mechanicalmeans; for example, this step can be performed via a mechanical handleror via an edge guide that “roughly” positions the substrate to a desiredprinting position, per numeral 211. The printer then detects actualsubstrate position using a precision detection system, per numeral 213;in one embodiment, this is performed using a high-precision camera thatimages a region of a fiducial (known pattern in or on the substrate),with the camera being precisely positioned relative to the print system,and with position detection software used to perform image processing soas to identify exact position of the fiducial, e.g., to the nearestmicron. Advantageously, the fiducial can be a two-dimensional pattern orset of patterns, enabling a determination of rotational orientation ofthe substrate, and/or scale and/or skew; the more complex the fiducial(or the greater the number of independent features recognizable), thegreater the accuracy and/or number and/or complexity of alignment orposition issues that can be corrected. To provide an example of this,one embodiment (see FIG. 9A, also discussed below) contemplates thatevery panel on a substrate will have at least two dedicated alignmentmarks, enabling per-panel error detection or error mitigation on a panelbasis; this is not required for all embodiments. Whichever the detectionmechanism, the computer (and/or one of its processors) then derivesdeviation between (1) detected panel position, dimension andorientation, and (2) expected panel position, dimension and orientation,and it adapts the print job as necessary to register printing with anyunderlying layers and/or product geometry (215). Per numeral 217, thepanel is then unloaded from the printer and is optionally cured pernumeral 218. As indicated by reference numeral 219, a new substrate canthen be loaded for a new print job.

As an example representing a hypothetical print process for OLED orsolar panel manufacturing, a typical layer thickness for a panel mightbe on the order of sub-micron to hundreds of microns, depending on theparticular layer that is to be “printed” (and then cured or otherwiseprocessed); array definition information might be received and used todetermine printing location for each panel according to a recipe for thespecific panel linked to that location. In configuration with 15 panelsper substrate, for example, array definition information might bereceived to indicate that a first panel “recipe” was to be reproducedfive times in each of the first two rows of panels on the substrate(i.e., each at precise locations) and that a second unique panel recipewas to be reproduced five times in a third row of panels (i.e., atprecise locations, assuming a second recipe different from the firstrecipe). The array definition in this example would identify each panellocation and the specific recipe to be used for that location. Note thatthe example of a homogeneous, continuous layer for any given product isillustrative only; in some embodiments, layers may be patterned withineach product (as opposed to being a homogenous coating, such as a thinfilm encapsulation for a particular product or panel), or thickness canbe varied within a layer as defined by the particular panel recipe.Continuing with a fifteen panel, three-row example, the third row ofproducts could potentially feature a different layer thickness, withdenser halftoning used to “build” a thickness greater than created forthe first two rows of panels.

FIG. 2B provides a flowchart 221 of an exemplary printing process foreach substrate in a series of substrates. More specifically, as each newsubstrate is received in the series (223), a mechanical handlertransports the substrate to a first position (225); this positions thesubstrate in a manner where an expected fiducial position falls within afield of view of a camera. In one embodiment, per numeral 227, one ormore cameras can be used to capture fiducial position. For example, oneprocess discussed below in conjunction with FIG. 9B uses a standardcamera to first identify the coarse position of the fiducial, and thesubstrate and fiducial are then repositioned as necessary for imagecapture using a second, high-resolution camera, i.e., to identifymicron-scale position of the fiducial. FIG. 2B illustrates in dashedline several optional processes 229 and 231, i.e., in which a substrateis repositioned to permit capture of multiple fiducials; as noted, themore fiducials and alignment features used, the greater the ability todetect non-linearities of the substrate or of individual panels. In thisembodiment, the substrate is controlled by a precision handler toeffectively transport fiducial(s) for each panel to the camera, but inalternate embodiments, the camera can be mounted to a motion system andcan be transported relative to a motionless substrate to locatefiducials, or both the substrate and the camera can be moved, as in thecase of split-motion axes. As noted by text at the left side of theFIG., another embodiment uses a line scanner to image the substrateand/or its fiducials during substrate loading or other transport; stillother embodiments feature a camera mounted to the printhead (i.e., usedfor very frequent “continuous” error monitoring and correction) andstill another embodiment uses non-visual detection mechanisms.Irrespective of number of fiducials and/or detection mechanisms, onceposition particulars are identified and any errors ascertained (233),the stored template is retrieved (235) and rendered. FIG. 2B illustratesthat the stored template can be in the form of a recipe (236), a bitmap(237) or in some other form (238) (e.g., object, vector or otherformat). Offset, misorientation and/or other error can be ascertained ona linear basis (239), using a least squares fit (LSF) approach (240) orusing some other type of error estimation mechanism (241). For example,one embodiment uses two fiducials per panel; the fiducials can be in theform of a complex shape (e.g., such as the “crosses” depicted by FIG.9A) and are used to determine panel rotation, corner offset and X and Yscaling error across a given panel. Then, printer control data can beadjusted or rendered from the template using linear or affinetransforms. For a LSF approach, non-linear error within a panel oracross a substrate can be detected and modeled by a polynomial in one ormore dimensions, e.g., a supervisory processor operating under thecontrol of software fits a curve to detected error (e.g., using errormeasures relative to multiple fiducials). Then, adjustment is performedaccording to the polynomial equation or an affine transform to assignprinter grid firing decisions and associated nozzle parameters. Armedwith a mechanism for mapping (242) the template to actual substrateposition, a supervisory processor then optionally assigns processingtasks to additional processors (e.g., cores of a multi-core processor).In one embodiment, a multicore processor having a dozen or moreprocessing cores are used to divide the rendering (or transformation)task, to speed processing; in another embodiment, hundreds of cores areused, further accelerating the processing. Such parallel processing isoptional, as implied by the use of dashed-line functional box 243.Irrespective of whether parallel processing is used, the system proceedsto render the printer control data in a manner dependent on detectedsubstrate and/or panel position, rotation, skew and scale, and assignsraster scans as appropriate (245). As implied by a first optional step,seen at the right side of FIG. 2B, in one embodiment (246), up-to-dateexpected droplet particulars for a given nozzle-waveform are supplied(e.g., mean and standard deviation of droplet volume and two-dimensionaldroplet trajectory for each unique waveform used for each uniquenozzle). This information is used in the rendering process in a mannercalculated to produce precise volume fills or ensure homogenousdistribution of ink; as will be discussed below, in one embodiment, thisdata is continuously remeasured (e.g., in between substrate prints) soas to develop robust measurement populations and account for variationsin properties of the deposited liquid (e.g., as a function of viscosity,ambient temperature and other factors). In one embodiment, as notedearlier, scan paths are not adjusted in response to misregistration,while only nozzle/droplet firing parameters are changed. In anotherembodiment, per numeral 247, rasterization is reassessed and isre-optimized; for example, as nozzle firing data changes, it may bepossible to perform fewer scans (or conversely, it might be advisable toadd scans for optimal control over deposited droplet volumes andpositions. Numeral 247 denotes that, in one embodiment, printheadoffsets from scan-to-scan can be reassessed as necessary. Per numeral248, a consistency check can also be performed on printer control datathat has already been partially adjusted from a spatial perspective toaddress error; for example, in one embodiment, printer control data isfirst rendered in dependence on detected substrate-to-printer variationand, subsequently, a software process is called to identify fluidicwells (or other discrete regions of the substrate) and “check” inkdensities and fills for those regions—if transformation would result intoo much or too little ink being deposited, the software process smoothsor otherwise adjusts the printer control data to eliminate the error,thereby maintaining aggregate ink fills and ink density within desirednorms. In yet another embodiment, the “edges” of a continuous layer(e.g., an encapsulation layer) are assessed following error adjustmentin order to maintain a desired edge profile (249); that is, due to thespreading nature of deposited fluid, it might be desired toincrease/decrease ink density at layer edges to main homogenous layerthickness up to the intended layer boundary, and edge characteristics insuch an embodiment can be assessed or adjusted after error processingthat spatially transforms printer control data to address error. Edgeprocessing, as referenced, represents another type of consistency check,and is discussed extensively in the aforementioned U.S. ProvisionalApplication No. 62/019,076, i.e., see generally, FIGS. 7A-7E. Note thatwhile this provisional application discusses use of the mentionedtechniques for encapsulation layers, these teachings can be applied toenhance accuracy in any deposited layer, patterned or otherwise. Manyvariations of these principles will occur to those skilled in the art.Finally, when processing is complete, the rendered printer control dataincluding any raster scan information is sent to the printer, and themethod ends, per numerals 251 and 253. As noted earlier, in oneembodiment, it is generally desired to perform this processing persubstrate in approximately two seconds or less for each substrate orpanel that is processed by the system.

As noted earlier, layer information may be received, stored and renderedin many forms. FIG. 2C provides an example of a “recipe editor” that canbe used to generate and edit layer descriptions in order to define“ideal” printing. Such data can be saved (with or without some form ofpre-processing) in order the generate template data that will beadjusted or transformed for each new substrate.

More specifically, FIG. 2C shows a screen shot 261 of a software userinterface (“UI”) that provides for panel recipe definition or editing.Such a UI could be used in a manner integrated with a printer ormanufacturing system, at an earlier design time (e.g., as part of acomputer aided design system), or in some other manner. As representedby the screen shot 261, a software application advantageously simulatesthe layout of a substrate or print area and provides mechanisms forediting that layout. A UI display region 263 seen at the left side ofthe screen shot encompasses three different panel sizes variouslyembodied amongst the six depicted panels. In this example, each of thethree different panel sizes will have a respective recipe. A second UIdisplay region 265, seen at the bottom right of the screen shot,provides a window for array definition, and permits identification ofCartesian position for each of the depicted six panels, including“Sub-panel1,” “Sub-panel2,” “Sub-panel3,” “Sub-panel3H1V0,”“Sub-panel3H0V1,” and “Sub-panel 3H1V1” as well as a link (for eachpanel) to a corresponding recipe (in this case, effectuated by thesenames, e.g., “Sub-panel3;” the latter three panels (Sub-panel3H1V0,”“Sub-panel3H0V1,” and “Sub-panel 3H1V1”) all use the same recipe(“Subpanel3”) but feature respective horizontal and vertical offsetrelative to the substrate. A topmost one of these definitions is seenexpanded (i.e., because it is “selected”). Note that the second UIdisplay region 265 provides for graphical selection and removal of anygiven panel (right side) as well as for expansion and manipulation ofdata for any desired panel (such as for panel1, as illustrated); forexample, FIG. 2C shows that the topmost panel, “Sub-panel1,” is definedto have a size of 825 by 500 millimeters, to have its top left cornerpositioned at 50 millimeters each from the left and top edges of theprintable substrate area, and to have selective corner rounding (i.e.,via a selected “corner radius” value). The expected position of one ormore fiducials can be identified using a third UI display region 269; asnoted earlier, printing is effectively defined relative to suchfiducials, such that printing (and print area for any given panel) canbe rendered based on deviation between expected fiducial position(relative to the printer or print transport path) and any actual (i.e.,detected) fiducial position for the specific panel. As implied by thescreen shot 261, different fiducials or fiducial feature points can beidentified, e.g., to detect scaling error or skew. If desired, in otherembodiments, the third UI display region 269 can be configured to acceptdefinition of a fiducial shape or substrate feature, which the softwarethen attempts to match to a detected (imaged) shape identified on eachsubstrate at run-time. Finally, the UI is seen to provide for a fourthUI display region 267 which permits definition of substrate size andthickness. While in one embodiment, the printed layer thickness iscommon across all panels (e.g., for each layer of respective panels),this need not be the case for all embodiments; in one contemplatedembodiment, thickness can vary per panel and can be influenced usingdifferent localized halftoning densities. For each layer, printing isperformed as an integral print job across the substrate, e.g., viamultiple scans, and the substrate and its wet ink are then transportedto a cure chamber to produce a permanent layer; this post-printing cureprocess is typically also performed within a controlled atmosphere toinhibit particulate, oxygen or moisture contamination. Other layers canbe added after the deposited liquid is cured or otherwise hardened.

As noted earlier, layer data defined, e.g., using a recipe editor can bestored in a myriad of forms suitable to the embodiment, e.g., as abitmap, as raw recipe data, using a vector representation or in someother manner. In one embodiment, the recipe data is used to create agrayscale image (e.g., an array of 8 bit values for each position on thesubstrate) where each grayscale value in the image denotes a density ofink that is to be applied in the corresponding substrate position, andwhere each grayscale value is used to generate localized halftoning(i.e., according to the print grid) to build layer thickness. An examplehere would be helpful; in one embodiment, a matrix of eight-bitgrayscale values is defined with rows and columns of eight-bit valuesbetween “0” and “255.” Each value, e.g., “235,” corresponds to a unitarea of the substrate and maps to a specific layer thickness. Forexample, the value “235” might (depending on process and materials) mapto a thickness of seven microns in the finished layer. If all thegrayscale values in the matrix shared the same value, this might map toa relatively homogeneous layer, but the values can be varied to varythickness across a panel, fill in underling geometries (e.g., structuralvoids beneath the layer), to tailor edge buildup, or for any desiredeffect. Grayscale value assignment can either be “dead-reckoned” todesired thickness (with variable, localized halftoning selecteddependent on ink and process parameters in a manner that adapts thegrayscale value to the desired thickness) or can be calibrated inadvance to the desired thickness (with halftoning bearing a fixedrelationship to grayscale values). In one embodiment, the correlationbetween grayscale value and thickness is measured after test layerformation (e.g., after cure or drying), so that deposited ink density isclosely tied to ultimate layer thickness. Based on the measured data (orother feedback), software can then map droplet density to a desired gridpitch, for example, using the formula:

${{Desired}\mspace{14mu} {Thickness}} = {h \times \left\{ \frac{{Volume}_{drop}}{{Pitch}_{{in} - {scan}} \times {Pitch}_{{cross} - {scan}}} \right\}}$

In this formula, the in-scan pitch represents the spacing between dropopportunities in a first direction of relative motion between theprinthead and substrate, the cross-scan pitch represents the spacingbetween drop opportunities in a direction generally perpendicular to (orotherwise independent of) this first direction, and the parameter h(times 100) is the grayscale value in percentage. In one embodiment,this relationship can vary over time and, thus, ink particulars can becontinually remeasured to develop robust empirical data, for dynamicfactors such as process or temperature, for specific machine or inkparticulars, for nozzle age, or for other factors, with weightingemphasizing the most recent measurements. Clearly, many examples arepossible, and as this example indicates, many different types ofprocessing can be performed, either to generate a “template” from recipedata, or at run time to render a print job from a template depending ondetected error.

FIGS. 3A-B and FIGS. 4A-G are used to discuss various renderingprocesses. As variously noted above, in one embodiment, errorrepresenting linear distortion of the entire substrate or panel can bedetected and corrected for and, in another embodiment, errorrepresenting nonlinear distortion of the entire substrate or any panelcan be detected and corrected.

FIG. 3A presents a flowchart 301 where, to adjust for detected error, amapping between detected panel geography and the print grid is firstdefined (303). This mapping is generated to adapt rendering of aninstance of a stored “template” (or raw layer data) to detecteddistortion. For example, referring briefly back to FIG. 1B, in the eventof substrate positional offset, such a grid will be used to define pixelfiring patterns relative to actual panel position (i.e., adapting toerror) in a manner corresponding to the offset vector 123. In the caseof the example of FIG. 1C, the mapping will identify or designate aportion of the print grid of sufficient size to represent the printimage rotated by angle α; in the case of the example of FIG. 1D, themapping is of sufficient size to receive printing scaled by (k₁)X and(k₂)Y. Generally speaking, the transformation is defined so as toencompass the desired, printable area of the specific run of the productarray or substrate; for example, if substrate distortion increases ordecreases substrate scale relative to the template print image, then theprint grid might feature more or fewer nozzle positions representingincreased, decreased or shifted area. The transformation is then used torender print data in a manner that registers with any substrate (e.g.,panel) error. For example, if a pre-rendered template is stored forrepeated print runs, then this template can be transformed (i.e.,rotated, scaled, offset, skewed, etc.) in a manner corresponding to themapping (and thus corresponding to the error) in a manner that adaptsthe print image to any detected per-run positional or alignment error.This transformation is performed by identifying that portion of theprint grid corresponding to detected panel position (305), and thenmodifying the cached template data in a manner that utilizes theidentified grid points but that is adjusted for detected error. Forexample, in one embodiment, as referenced by numeral 307, ifpre-processing generated firing decisions of P(x,y) for each point onthe print grid, then modified printer control data for nodes of theprint grid that match detected product position can be determined independence on a positional error vector and analysis of one or more ofthe pre-processed firing decisions. This dependence can be formedrelative to a closest node of the template data (308), offset accordingto an error vector or, because misalignment or positional error can be anon-integer multiple of grid pitch, a weighted function of 2, 3, 4 or adifferent number of filing decisions from the template (309). In oneembodiment, the firing decision is based only on a single node of printgrid represented by the original template (i.e., offset according to theerror vector), and in a second embodiment, it is based on a weightedaverage of four closest nodes, according to

P′(x′,y′)=fn{P _(nw)(x,y),P _(ne)(x+1,y),P _(sw)(x,y+1),P_(se)(x+1,y+1),

where P_(nw)(x,y), P_(ne)(x+1,y), P_(sw)(x,y+1), and P_(se)(x+1,y+1)respectively represent northwest, northeast, southwest and southeastgrid point decisions, and where x and x′ and y and y′ are relatedaccording to detected error. Clearly, this is but one error compensationalgorithm and many alternate algorithms will readily occur to oneskilled in the art.

For example, if a hypothetical grid point {P′(x′,y′)} (representing aspecific grid point for the transformed panel), given error, correspondsto a point that is closest to each of specific NE and SE grid points(print pixels) of the cached template, and less close to specificcorresponding NW and SW grid points (print pixels), and if these NE, SE,NW and SW points respectively corresponded firing decisions of (1, 1, 1and 0), then the print grid point {P′(x′,y′)} could be assigned a binaryfiring decision (1 or 0) as a function of firing decisions (1, 1, 1 and0) weighted according to error distance to these four nodes {e.g.,assigning a firing decision of “1” to P′(x,y′)} according to{0.40*(1)+0.40*(0)+0.10*(1)+0.10*(1)=0.60>0.50}. Note again that thismathematical relationship is exemplary only and that many algorithms canbe used for assigning nozzle firing decisions; as noted, in onespecifically contemplated embodiment that uses a cached template, thefiring decision is based only on a closest single overlapping printpixel from the transform image, with a software antialiasing processused to process nozzle firing decisions to ensure a consistent number ofdroplets in the transformed image. In one embodiment, as mentioned, anaffine transform is used. Irrespective of correction methodology, aserror-adjusted printer control data is created, it is stored in memoryas a new or customized print image (311) with finished, rendered printercontrol data being sent to the printer (313) for execution. Followingcompletion of the layer (317), the system is then prepared for anensuing layer (e.g., using the same transformations) or a new productrun or substrate.

Note that numeral 310 refers to a dashed line (optional) wrap processused to ensure consistency of deposition. For example, if a particularpoint P′(x′,y′) were to fall within a fluidic well used to retain liquidfor use as a light generating layer of a display, and a weighted errorfunction were to call for reliance on template print pixels that felloutside of that well relative to the template image, the weightedfunction could be shifted (i.e., wrapped) so as to instead rely on otherprint pixels associated with the unshifted print well. Such a wrapprocess can also optionally be performed for each core or processor in aparallel processing environment, e.g., borrowing print pixels of otherprocessors in order to maintain localized consistency. Other examplesare also possible. For example, numeral 313 indicates that in someembodiments, the template image is shifted or distorted according toerror, and that a software daemon is then called to processpredetermined regions of the substrate (e.g., fluidic wells) and testfor compliance within a threshold. One such process (i.e., antialiasing,314) includes simply testing the number of droplets (or aggregateexpected volumes from stored data representing the respective droplet'smean volumes) to ensure that aggregate liquid still meets required normsfollowing error shifting. In another variation, nozzle data such asvalidation data, expected droplet volumes or trajectories or other datacan be tested by such a daemon to ensure desired aggregate valueconsistency, 315 (e.g., to facilitate layer homogeneity), withadjustment to printer control data being performed as necessary toprovide for deposition consistency. As noted, many different processescan be used.

FIG. 3B illustrates another flowchart 351 used to describe processing ofa stored template. More specifically, information representing thedesired layer is first loaded from the template (353). In oneembodiment, this information includes raw recipe data, in a secondembodiment, the information includes a bitmap representing nozzle firinginstructions, and in a third embodiment, the information is representedby some other format, e.g., intermediate to these two forms. The systemthen calculates transformation parameters (355) needed to map printingrepresented by the template over the actual (detected) panel orsubstrate position; these parameters are then applied to generate atransformed representation (357). As implied by optional process block359, in one embodiment, rendering of printer control data can beperformed at run time directly on recipe data (i.e., stored as thetemplate) according to transformation parameters. As noted, in oneembodiment, one or more affine transforms can be used (360). Thetransformed representation is then output as a rendered bitmap (361) andused to produce raster data (363). The transformed representation can bechecked for consistency of ink density or aggregate volume for a unitarea or for other quality control reasons (363). Subject to anycorrected, this data is then output to the printer (363) and the methodends (365).

FIG. 4A provides an example 401 used to explain one example print gridand transformation as applied to a cached bitmap. A print grid for anideal (i.e., no error) “bitmap” print image is referenced by numeral403; each “box” in that print grid (e.g., per numeral 404) represents aprint “pixel” defined by a grid point, where an “X” in the box denotesthat a print nozzle is to fire a droplet at the corresponding grid pointas a printhead is moved relative to the underlying substrate. Similarly,a “box” or pixel 405 seen as empty (i.e., not having an “X”) denotesthat a print nozzle will not be fired over that position. The top ofFIG. 4A shows a representation of a printhead 407 where individualtriangles (such as identified by numeral 409) represent each nozzle. Asthe printhead moves relative to the substrate, each given nozzle willpass a series of print pixels (discrete droplet firing points), each ata different point in time. As an example, nozzle 410 will pass as it ismoved downward relative to the drawing page an area corresponding toprint pixel 404 (where it is fired) and subsequently an areacorresponding to print pixel 405 (where it is not fired). The bitmap 403is predefined and is stored in memory as a template for use in arepeatable manufacturing process.

FIG. 4B presents an example 411 where an instance of a product is deemedto be at an offset position relative to the template, for example, dueto positional error in a substrate. Because of this offset (413), thearea that should receive printing for accurate registration isrepresented by numeral 412. If the nozzle firing instructions providedby the ideal print image 403 remain unadjusted, then printing will occurin a manner that is misaligned with underlying product geometry. It istherefore desired to adjust the template so that printing occurs in theright place. In this regard, the template from FIG. 4A can be distortedat run time (e.g., by shift in position) so as to be dynamically alignedwith an individual substrate, panel or other product region so as tomitigate error.

FIG. 4C provides an example 421 of a portion of the print grid 422 whichoverlays detected product position. Note that in this embodiment this isthe same print grid as represented by FIG. 4A but with nodes thatcorrespond to detected product position. Once again, each depicted nodedefines a print pixel that will be passed by the printhead 407 in itsmotion relative to the substrate, and each “box” (such as print pixel419) corresponds to a printhead nozzle and a nozzle firing time. In oneembodiment, the specific nozzle is predetermined (e.g., scans associatedwith the template will also be used for the specific product instance),but this is not required for all embodiments. However, note that thepositional offset (413) may not exactly align with printhead nozzlein-scan or cross-scan pitch. Software therefore effectively overlaysdetected product position against the print grid 422 and bases firingdecisions for this overlay on a shifted version of the original templateimage according to offset 413; each print pixel in this example maycorrespond to (overlay) up to four print pixels of the original templateprint image depending on the offset 413.

For example, FIGS. 4B and 4C show two cases where a print pixel 419 fordetected product position corresponds (given error 413) to a pointintermediate four/two template print pixels, as denoted by numerals 415and 417. Note that for various embodiments, any number of nearby pixelscan be applied in the weighting function; in one embodiment, only asingle “closest” pixel only is used, in a second embodiment, “two”neighboring pixels can be used (e.g., per numeral 417) while in a thirdembodiment, a different number of nearby pixels (e.g., “9”) can be used,i.e., the disclosed techniques should not be viewed as limited toconsideration of a weighted average of four template print pixels. Thetwo print pixel example 417 serves as a proxy for any number of pixels,whether more than, less than or equal to two, and whether or not basedon a weighted average of multiple pixels. A decision is made for printpixel 419 based on the referenced pixel set, and once performed forevery grid point seen in FIG. 4C, this effectively “transforms” the datafrom FIG. 4A to correspond to actual product position. Once this processis complete, then rasterization (e.g., scan planning) is performed, asappropriate, and printing is then executed based on the detected productposition. The above process accurately maps any ink densitiesrepresented by the original template print image onto the shiftedproduct geometries as detected in the particular print run.

FIGS. 4D and 4E provide examples 431 and 441 that respectivelyillustrate bitmap processing in the event of unintended product (array,product, substrate or panel) rotation. As seen in FIG. 4D, it is assumedthat a substrate or portion thereof is misoriented by angle α, pernumeral 435. For proper printing, the print nozzle firing pattern shouldtherefore also be distorted according to this same value, as representedby outline 433. FIG. 4E highlights a print grid region corresponding todetected product/panel position. Note that while the desired print areais rotated relative to the substrate, the printhead 407 and nozzles(such as nozzle 409) will each define a regular print grid at whichdroplets can be fired. Once again, for each grid point (or print pixel)of the print grid, the software shifts and overlays the originaltemplate image and then weights any overlaid print pixels of theoriginal template in order to obtain a weighted pixel firing decisionfor that grid point. This operation is represented for example withreference to print pixel 443 in FIG. 4E, and to associated(illustrative) processing of four template grid points 445 or twotemplate grid points 447. Once again, the two grid point example 447 iscited simply to indicate that alternative embodiments can use any numberof references to the cached template print image.

FIGS. 4F and 4G provide examples 451 and 461 that respectivelyillustrate processing in the event of scaling error. Once again, numeral403 refers to the template for a particular geography, and numeral 455represents a footprint that should receive printing to properly align anew layer with the desired product footprint according to a scalingvector 457. In such an example, a new print grid is effectively definedaccording to the scaling vector by a mathematical multiplicationprocess. Note that the print grid, in addition to effectively beingscaled in size, also potentially uses variable offsets according tosubstrate position. Assuming an increase in both dimensions to thefootprint for a product or panel that is to be printed, the effect is asif the pixels of the overlaid template image are increased in size(e.g., compare the depicted size of template print image pixels 465and/or 467 as represented in FIG. 4G to the print image pixels 445 and447 depicted in FIG. 4E).

FIGS. 4H and 4I show an illustration directed to skew compensation.Numeral 475 represents a footprint that should receive printing toproperly align a new layer with the desired product footprint accordingto a skew adjustment formula 477. Note that the amount of skew variesaccording to height of the subject that is being distorted. If the errorbeing compensated for corresponds to uniform skew across the substrate,then the amount of distortion in the “Y” dimension (left to right acrossthe FIG.) varies depending on the “X” dimensional value taken from thesubstrate edge. The X coordinate transformation in this example is unity(i.e., no change), but note that in general, this result will differdepending on the orientation of skew. The template is scaled accordingto a scaling vector by a mathematical multiplication process accordingto formula 477, and is effectively overlaid against a print gridcorresponding to detected product scale; the firing value for each printgrid point of the overlaid grid is computed according to formula 477(i.e., the inverse of the scaling), based (e.g.) on 1, 2, 4 or anothernumber of overlapping or nearby print pixels according to a weightingcriteria; this is represented in FIG. 4I by the depicted matching ofprint grid point 483 against weighted, positionally overlaid printpixels 485 or 487 of the template; again, note that each grid pointrepresents a possible firing position of a nozzle (e.g., referenced bynumeral 409) of a printhead 407 as it is moved vertically relative tothe drawing page.

Note that in the depicted examples, there are print pixels adjacent theedge of the footprint of the print grid that are not necessarilyweighted by a consistent number of template print pixels (e.g., 4)relative to other parts of the print grid. To avoid underrepresentationof droplets adjacent a border region of the new footprint, an edge gridpoint can advantageously use an algorithm (e.g., wrapping of pixels fromthe opposite side of the footprint) to ensure proper droplet density. Ina situation where the depicted footprint (e.g., 475) represents theboundaries of the desired layer, then an edge process (e.g., fencing)can be applied if desired to ensure well-defined edges, as previouslyreferenced. Other techniques and variations are also possible.

It was earlier mentioned that in one embodiment, a bitmap can consist ofgrayscale values (e.g., 8 bit or other multibit values) where each valuerepresent a volume of ink or desired thickness. The processing justdescribed can also be applied to such grayscale values simply byweighting each grayscale value of the template by the appropriatedistance measures and grayscale magnitude. For example, again using theexample of a hypothetical grid point {P′(x′,y′)} of detected productgeometry that, according to normalized overlapped area, maps 40% to eachof the NE and SE grid points (print pixels) of a template, and 10% of NWand SW grid points of that template, and if the NE, SE, NW and SW pointsrespectively had grayscale decisions of (235, 235, 150 and 0), then thehypothetical grid point {P′(x′,y′)} could be assigned a grayscale valueof 203 according to {0.40*(235)+0.40*(235)+0.10*(150)+0.10*(0)=203}.This measure can also, if desired, be directly converted by software forindividual print grid notes to a binary firing decision via comparisonwith any desired threshold (e.g., “1”=fire if 203>Th). Note that theserelationships are exemplary only and that many algorithms can be usedfor assigning nozzle firing decisions in a customized print image; asnoted earlier, in at least one contemplated system, measured per-nozzle,per-drive waveform droplet particulars can be factored into this process(e.g., the fact that a nozzle corresponding for P′(x′,y′) fires a heavydroplet, e.g., volume=12.4 pL, assuming a given printhead scan offset,could be relied upon in assigning a different nozzle to instead fire thedroplet for P′(x′,y′) or conversely, scans can be replanned so as to usea different printhead offset and thus a different nozzle for P′(x′,y′)).Other variations are also possible.

With methods for transforming a print image introduced, this disclosurewill now discuss some exemplary circuitry associated with printing andprintheads used in an industrial printer to fabricate one or more layersof a product.

In FIGS. discussed above, a simplified printhead (e.g., referenced bynumeral 407 in FIGS. 4A-I) was depicted as having a relatively smallnumber of nozzles, e.g., 20 or so. In fact, for a typical manufacturingoperation, especially for large scale products, a printhead might have amuch greater number of nozzles, e.g., thousands, arranged in multiplerows; there can be multiple such printheads mounted to a commonassembly, e.g., such that, in all, thousands to tens of thousands ofprint nozzles are used to jet material across a relatively wide swath ofthe substrate. This structure provides for high quality ink dropletdelivery with highly accurate positional resolution. Each printhead isexpected to deposit a nominal amount of ink per droplet (e.g., tenpicoliters, or 10.00 pL), but in practice, this number can vary fromnozzle-to-nozzle, as can nozzle position, droplet velocity, and dropletejection trajectory. These variations can potentially cause defects in adeposited layer if left unchecked, defects which can carry over to thequality of a finished product.

In one embodiment, in order to more accurately fabricate the desiredlayer, droplet particulars for each nozzle are measured and used todevelop a statistical model for each nozzle's performance for each ofthese parameters; repeated measurement helps effectively average outmeasurement error, and develop a relatively accurate understanding of amean and sigma for each parameter. Various techniques are used toaddress the variations referred to above; generally speaking, thesetechniques leverage the variations, providing for precisely planneddroplet depositions aimed at achieving specific ink fills, ink filldensities, and droplet distribution based on measured per-nozzle orper-droplet means and associated sigmas. Halftoning (i.e., ink density)and/or template adjustment can incorporate (or be corrected for) suchvariation such that, malfunctioning nozzles and/or variations in dropletposition and/or volume can be corrected for. Note that “halftoning” asused herein refers the varying the droplet density (e.g., number ofdroplets per group of print grid nodes) to influence layer thickness,i.e., even though “tones” are not used per se (i.e., the “ink” ordeposited liquid is typically colorless). In one technique describedbelow, multiple (alternative) electric drive waveforms are madeavailable for selection on a per-nozzle basis to provide for a selectiveability to vary/deliver a targeted droplet volume and position(including at least one choice that approximates an ideal target dropletvolume and position). The statistical measurements can be performed foreach such waveform, and for each nozzle, so as to provide high accuracyin planning; these measurements can be updated or reperformed over time,so as to accommodate changes in ink properties (e.g., viscosity),account for temperature change, nozzle clogging or age, and otherfactors. In the sections below, the measurement capabilities to providethis understanding are introduced. Reflecting briefly on the earlierdiscussion relating to use of a print grid, each grid point will beassociated with a nozzle of a printhead; the measurement capabilitiesjust referred to can be applied in this process, such that for example,a malfunctioning nozzle is not assigned a firing decision in a printheadpass (and/or so that any required droplets are redistributed to othernozzles). In addition, differences in “X” axis position of a droplet canbe corrected through the use of the alternate nozzle drive waveformsreferred to, or through tuning or amplifying a preselected waveform, soas to change droplet timing to better position droplets or change theirvolume. Substantial additional detail on these practices is provided inthe patent applications referred to earlier (which have beenincorporated herein by reference).

FIGS. 5A-5D are used to introduce control over nozzle firing and drivewaveform selection.

Typically, the effects of different drive waveforms and resultantdroplet volumes are measured in advance. In one embodiment, for eachnozzle, up to sixteen different drive waveforms are then stored in aper-nozzle, 1 k static random access memory (SRAM) for later, electiveuse in providing discrete volume variations, as selected by software.With the different drive waveforms on hand, each nozzle is theninstructed droplet-by-droplet as to which waveform to apply via theprogramming of data that effectuates the specific drive waveform. Thisconfiguration information is stored separately by a printer (or controlprocessor) from the firing decisions that will be applied to asubstrate.

FIG. 5A illustrates one such embodiment, generally designated by numeral501. In particular, a processor 503 is used to receive data definingintended fill volumes per target region for a particular layer ofmaterial that is to be printed. As represented by numeral 505, this datacan be a layout file or bitmap file that defines droplet volumes pergrid point or positional address. A series of piezoelectric transducers507, 508 and 509 generate associated ejected droplet volumes 511, 512and 513, that are respectively dependent on many factors, includingnozzle drive waveform and print-head-to-print-head manufacturingvariations. During a calibration operation, each one of a set ofvariables is tested for its effects on droplet volume, includingnozzle-to-nozzle variation and the use of different drive waveforms,given the particular ink that will be used; if desired, this calibrationoperation can be made dynamic, for example, to respond to changes intemperature, nozzle clogging, nozzle age or other parameters. Thiscalibration is represented by a droplet measurement device 515, whichprovides measured data to the processor 503 for use in managing printplanning and ensuing printing. In one embodiment, this measurement datais calculated during an operation that takes literally minutes, e.g., nomore than thirty minutes for thousands of nozzles and preferably muchless (e.g., for thousands of printhead nozzles and potentially dozens ofpossible nozzle firing waveforms), as an offline process. In anotherembodiment, such measurement can be performed iteratively, that is, foreach nozzle, in a manner that updates different subsets of nozzles atdifferent points in time (e.g., in between successive substrates in anassembly line process, as substrates are being loaded and unloaded). Anon-imaging (e.g., interferometric) technique can optionally be used,potentially resulting in dozens of droplet measurements per nozzle,covering dozens to hundreds of nozzles per second. This data and anyassociated statistical models (and means) can be stored in memory 517for use in processing layout data or a print image (e.g., bitmap data)505 when it is received. In one implementation, processor 503 is part ofa computer that is remote from the actual printer, whereas in a secondimplementation, processor 503 is either integrated with a fabricationmechanism for products (e.g., a system for fabricating displays) or witha printer.

To perform the firing of droplets for the depicted embodiment, a set ofone or more timing or synchronization signals 519 are received for useas references, and these are passed through a clock tree 521 fordistribution to each nozzle driver 523, 524 and 525 to generate thedrive waveform for the particular nozzle (527, 528 and 529,respectively). Each nozzle driver has one or more registers 531, 532 and533, respectively, which receive multi-bit programming data and timinginformation from the processor 503. Each nozzle driver and itsassociated registers receive one or more dedicated write enable signals(we_(n)) for purposes of programming the registers 531, 532 and 533,respectively. In one embodiment, each of the registers comprises a fairamount of memory, including a 1 k static RAM (SRAM) to store multiple,predetermined waveforms, and programmable registers to select betweenthose waveforms and otherwise control waveform generation. The data andtiming information from the processor is depicted as multi-bitinformation, and although this information can be provided either via aserial or parallel bit connection to each nozzle (as will be seen inFIG. 5B, discussed below, in one embodiment, this connection is serialas opposed to the parallel signal representation seen in FIG. 5A).

For a given deposition, printhead or ink, a processor chooses for eachnozzle a set of sixteen drive waveforms that can be electively appliedto generate a droplet; note that this number is arbitrary, e.g., in onedesign, four waveforms could be used, while in another, four thousandcould be used. These waveforms are advantageously selected to providedesired variation in output droplet volume and/or position for eachnozzle, e.g., to cause each nozzle to have at least one waveform choicethat produces a near-ideal droplet volume (e.g., a mean droplet volumeof 10.00 pL), and to provide a range of deliberate volume variation foreach nozzle. In various embodiments, the same set of sixteen drivewaveforms are used for all of the nozzles, though, in the depictedembodiment, sixteen, possibly-unique waveforms are each separatelydefined in advance for each nozzle, each waveform conferring respectivedroplet volume characteristics.

During printing, to control deposition of each droplet, data selectingone of the predefined waveforms is then programmed into each nozzle'srespective registers 531, 532 or 533 on a nozzle-by-nozzle basis. Forexample, given a target droplet volume of 10.00 pL, nozzle driver 523can be configured through writing of data into registers 531 to set oneof sixteen waveforms corresponding to one of sixteen different dropletvolumes. The volume produced by each nozzle would have been measured bythe droplet measurement device 515, with nozzle-by-nozzle (andwaveform-by-waveform) droplet volumes and associated distributionsregistered by processor 503 and stored in memory in aid of producingdesired target fills. This same process can be performed for dropletposition or trajectory. The processor can, by programming the register531, define whether or not it wants the specific nozzle driver 523 tooutput a processor-selected one of the sixteen waveforms. The processorcan also program the register to utilize a per-nozzle delay or offset tothe firing of the nozzle for a given scan line (e.g., to align eachnozzle with a grid traversed by the printhead, to correct for errorincluding velocity or trajectory error, and for other purposes); thisoffset is effectuated by counters which adjusts use of the particularnozzle (or firing waveform) by a programmable number of timing pulsesfor each scan. To provide an example, if the result of dropletmeasurement indicates that one particular droplet tends to have a lowerthan expected velocity, then corresponding nozzle waveform can betriggered earlier (e.g., advanced in time, by reducing a dead timebefore active signal levels used for piezoelectric actuation);conversely, if the result of droplet measurement indicates that the oneparticular droplet has a relatively high velocity, then the waveform canbe triggered later, and so forth. Other examples are clearlypossible—for example, a slow droplet velocity can be counteracted insome embodiments by increasing drive strength (i.e., signal levels andassociated voltage used to drive a given nozzle's piezoelectricactuator). In one embodiment, a sync signal distributed to all nozzlesoccurs at a defined interval of time (e.g., one microsecond) forpurposes of synchronization and in another embodiment, the sync signalis adjusted relative to printer motion and substrate geography, e.g., tofire every micron of incremental relative motion between printhead andsubstrate. The high speed clock (φ_(hs)) is run thousands of timesfaster than the sync signal, e.g., at 100 megahertz, 33 megahertz, etc.;in one embodiment, multiple different clocks or other timing signals(e.g., strobe signals) can be used in combination. The processor alsoprograms values defining a grid spacing; in one implementation, the gridspacing is common to the entire pool of available nozzles, though thisneed not be the case for each implementation. For example, in somecases, a regular print grid can be defined where every nozzle is to fire“every five microns.” This print grid can be unique to the printingsystem, the substrate, or both. Thus, in one optional embodiment, aprint grid can be defined for a particular printer with sync frequencyor nozzle firing patterns used to effectively transform the print gridto match a substrate geography that is a priori unknown. In anothercontemplated embodiment, a memory is shared across all nozzles thatpermits the processor to pre-store a number of different grid spacings(e.g., 16), shared across all nozzles, such that the processor can (ondemand) select a new grid spacing which is then read out to all nozzles(e.g., to define an irregular grid). For example, in an implementationwhere nozzles are to fire for every color component well of an OLED(e.g. to deposit a non-color-specific layer), the three or moredifferent grid spacings can be continuously applied in round robinfashion by the processor. Clearly, many design alternatives arepossible. Note that the processor 503 can also dynamically reprogram theregister of each nozzle during operation, i.e., the sync pulse isapplied as a trigger to launch any programmed waveform pulse set in itsregisters, and if new data is asynchronously received before the nextsync pulse, then the new data will be applied with the next sync pulse.The processor 503 also controls initiation and speed of scanning (535)in addition to setting parameters for the sync pulse generation (536).In addition, the processor controls optional rotation of the printhead(537). In this way, each nozzle can concurrently (or simultaneously)fire using any one of sixteen different waveforms for each nozzle at anytime (i.e., with any “next” sync pulse), and the selected firingwaveform can be switched with any other of the sixteen differentwaveforms dynamically, in between fires, during a single scan.

FIG. 5B shows additional detail of the circuitry (541) used in such anembodiment to generate output nozzle drive waveforms for each nozzle;the output waveform is represented as “nzzl-drv. wvfm” in FIG. 5B. Morespecifically, the circuitry 541 receives inputs of the sync signal, asingle bit line carrying serial data (“data”), a dedicated write enablesignal (we) and the high speed clock (φ_(hs)). A register file 543provides data for at least three registers, respectively conveying aninitial offset, a grid definition value and a drive waveform ID. Theinitial offset is a programmable value that adjusts each nozzle to alignwith the start of a print grid, as mentioned. For example, givenimplementation variables such as multiple printheads, multiple rows ofnozzles, different printhead rotations, nozzle firing velocity andpatterns and other factors, the initial offset can be used to align eachnozzle's droplet pattern with the start of the print grid, to accountfor delays and other factors. Offsets can be differently applied acrossmultiple nozzles, for example, to rotate a print grid or halftonepattern relative to substrate geography, or to correct for substratemisalignment. Similarly, as mentioned, offsets can also be used tocorrect for aberrant velocity or other effects. The grid definitionvalue is a number that represents the number of sync pulses “counted”before the programmed waveform is triggered; in the case of animplementation that prints flat panel displays (e.g., OLED panels), thetarget regions to be printed in presumably have one or more regularspacings relative to the different printhead nozzles, corresponding to aregular (constant spacing) or irregular (multiple spacing) grid. Asmentioned earlier, in one implementation, the processor keeps its ownsixteen-entry SRAM to define up to sixteen different grid spacings thatcan be read out on demand to the register circuitry for all nozzles.Thus, if the print grid spacing value was set to two (e.g., every twomicrons), then each nozzle could in theory be fired at this interval.The drive waveform ID represents is a selection value used to choose oneof the pre-stored drive waveforms for each nozzle. In one embodiment,the drive waveform ID is a four bit selection value, and each nozzle hasits own, dedicated 1 k-byte SRAM to store up to sixteen predeterminednozzle drive waveforms, stored as 16×16×4B entries. Briefly, eachwaveform can consist of sixteen discrete signal levels, of sixteenentries for each waveform contains four bytes representing aprogrammable signal level, with these four bytes representing a two-byteresolution voltage level and a two-byte programmable duration, used tocount a number of pulses of the high-speed clock. Each programmablewaveform can thus consist of (zero to one) discrete pulses to up tosixteen discrete pulses each of programmable voltage and duration (e.g.,of duration equal to 1-255 pulses of a 33 megahertz clock).

Numerals 545, 546 and 547 designate one embodiment of circuitry thatshows how a specified waveform can be generated for a given nozzle. Afirst counter 545 receives the sync pulse, to initiate a countdown ofthe initial offset, triggered by start of a new line scan; the firstcounter 545 counts down in micron increments and, when zero is reached,a trigger signal is output from the first counter 545 to a secondcounter 546; this trigger signal essentially starts the firing processfor each nozzle for each scan line. The second counter 546 thenimplements a programmable print grid spacing in increments of microns.The first counter 545 is reset in conjunction with a new scan line,whereas the second counter 546 is reset using the next edge of thehigh-speed clock following its output trigger. The second counter 546,when triggered, and activates a waveform circuit generator 547 whichgenerates the selected drive waveform shape for the particular nozzle.As denoted by dashed line boxes 548-550, seen beneath the generatorcircuit, this latter circuit is based on a high speed digital-to-analogconverter 548, a counter 549, and a high-voltage amplifier 550, timedaccording to the high-speed clock (φ_(hs)). As the trigger from thesecond counter 546 is received, the waveform generator circuit retrievesthe number pairs (signal level and duration) represented by the drivewaveform ID value and generates a given analog output voltage accordingto the signal level value, with the counter 549 effective to hold DACoutput for a duration according to the counter. The pertinent outputvoltage level is then applied to the high-voltage amplifier 550 and isoutput as the nozzle-drive waveform. The next number pair is thenlatched out from registers 543 to define the next signal levelvalue/duration, and so forth.

The depicted circuitry provides an effective means of defining anydesired waveform according to data provided by the processor 503. Ifnecessary to comply with print grid geometry or to mitigate a nozzlewith aberrant velocity or flight angle, the durations and/or voltagelevels associated with any specific signal level (e.g., a first, “zero”signal level defining an offset relative to synch) can be adjusted. Asnoted, in one embodiment, the processor decides upon a set of waveformsin advance (e.g., 16 possible waveforms, per-nozzle) and it then writesdefinition for each of these selected waveforms into SRAM for eachnozzle's driver circuitry, with a default selection of programmablewaveform to be applied responsive to a firing decision then beingeffected by writing a four-bit drive waveform ID into each nozzlesregisters.

The use of multiple signal levels to shape a pulse is further discussedin reference to FIG. 5C.

That is, in one embodiment, waveforms can be predefined as a sequence ofdiscrete signal levels, e.g., defined by digital data, with a drivewaveform being generated by a digital-to-analog converter (DAC). Numeral551 in FIG. 5C refers to a waveform 553 having discrete signal levels,555, 557, 559, 561, 563, 565 and 567. As noted for this embodiment, eachnozzle driver includes circuitry that receives and stores up to sixteendifferent signal waveforms, with each waveform being defined a series ofup to sixteen signal levels, each expressed as a multi-bit voltage and aduration. That is to say, pulse width can effectively be varied bydefining different durations for one or more signal levels, and drivevoltage can be waveform-shaped in a manner chosen to provide subtledroplet size variation, e.g., with droplet volumes gauged to providespecific volume gradations increments such as in units of 0.10 pL. Thus,with such an embodiment, waveform shaping provides ability to tailordroplet volumes to be close to a target droplet volume value; whencombined with other specific droplet volumes and positions, such asusing the techniques exemplified above, these techniques facilitateprecise fill volumes per target region. In another embodiment,predetermined waveforms can be applied with optional, further waveformshaping or timing applied as appropriate to adjust droplet volume,velocity and/or trajectory. In yet another example, the use of nozzledrive waveform alternatives provides a mechanism to plan volumes suchthat no further waveform shaping is necessary.

FIG. 5D shows yet another design 571. A CPU 573, for example, of amaster computer, sends print data (adjusted for error) to a print modulehaving multiple printheads (e.g., one of six different printheads, eachhaving hundreds of print nozzles). At the print module, an Ethernetconnection 575 receives the data from the CPU and provides that data toa field-programmable gate array (“FPGA”) 577. A customized “softprocessor” (578) within FPGA processes the data as appropriate andwrites that data to memory (i.e., dynamic random access memory or“DRAM”) 579. Unlike the embodiment described above, in the depictedembodiment, a waveform is written to memory for use by one or morenozzles; the particular format in which data is written or stored can bean implementation decision. For example, in one embodiment, the softprocessor 578 writes specific waveform as a series of drive levels (see,e.g., the discussion above in connection with FIG. 5C) for each nozzle;other FPGA logic 580 then reads this data out at the appropriate timeand provides this to amplifiers 581 and ultimately to the associatedprinthead 583 and associated nozzle drivers. In one implementation, thedepicted FPGA 577 and DRAM 579 are components of each printhead (e.g.,data is separately transmitted to each printhead), but this need not bethe case for all embodiments. Note that one function of logic 580 andamplifiers 581 are to place appropriate waveforms in parallel form,i.e., such that they can be read out together for each nozzle at theappropriate time, in parallel (as necessary or appropriate to thedesign). In one implementation, the DRAM 579 can optionally be organizedto have separate memory for each nozzle. Note that in this embodiment,instead of using a trigger, each nozzle receives one of sixteenwaveforms (i.e., with one waveform being a flat waveform or zero drivesignal, indicating that a particular nozzle is not to be fired). Theparticular drive waveforms can be dynamically supplied by the CPU 573 orwritten in advance (i.e., but dynamically changeable), with a run-time4-bit value used to provide nozzle firing decisions and associatedwaveform selection (and trigger output of that waveform from the DRAM579 or logic 580). Other alternatives are also possible.

With nozzle control circuitry thus introduced, as might be used in anexemplary manufacturing device, additional detail will now be presentedas to one possible implementation of such a device. As alluded toearlier, one contemplated implementation of the techniques describedherein is to the manufacture of flat panel devices in an array withthose devices then being cut from a common substrate. In the discussionbelow, an exemplary system for performing such printing will bedescribed, more specifically, applied to the manufacture of solar panelsand/or display devices that can be used in electronics (e.g., as smartphone, smart watch, tablet, computer, television, monitor, or otherforms of displays). The manufacturing techniques provided by thisdisclosure are not limited to this specific application and, forexample, can be applied to any 3D printing application and to a widerange of other forms of products.

FIG. 6A represents a number of different implementation tiers,collectively designated by reference numeral 601; each one of thesetiers represents a possible discrete implementation of the techniquesintroduced herein. First, techniques as introduced in this disclosurecan take the form of instructions stored on non-transitorymachine-readable media, as represented by graphic 603 (e.g., executableinstructions or software for controlling a computer or a printer).Second, per computer icon 605, these techniques can also optionally beimplemented as part of a computer or network, for example, within acompany that designs or manufactures components for sale or use in otherproducts. Third, as exemplified using a storage media graphic 607, thetechniques introduced earlier can take the form of a stored printercontrol instructions, e.g., as data that, when acted upon, will cause aprinter to fabricate one or more layers of a component dependent on theuse of different ink volumes or positions to mitigate alignment error,per the discussion above. Note that printer instructions can be directlytransmitted to a printer, for example, over a LAN; in this context, thestorage media graphic can represent (without limitation) RAM inside oraccessible to a computer or printer, or a portable media such as a flashdrive. Fourth, as represented by a fabrication device icon 609, thetechniques introduced above can be implemented as part of a fabricationapparatus or machine, or in the form of a printer within such anapparatus or machine. It is noted that the particular depiction of thefabrication device 609 represents one exemplary printer device that willbe discussed in connection with FIG. 6B, below. The techniquesintroduced above can also be embodied as an assembly of manufacturedcomponents; in FIG. 6A for example, several such components are depictedin the form of an array 611 of semi-finished flat panel devices, thatwill be separated and sold for incorporation into end consumer products.The depicted devices may have, for example, one or more light generatinglayers or encapsulation layers or other layers fabricated in dependenceon the methods introduced above. The techniques introduced above canalso be embodied in the form of end-consumer products as referenced,e.g., in the form of display screens for portable digital devices 613(e.g., such as electronic pads or smart phones), as television displayscreens 615 (e.g., OLED TVs), solar panels 617, or other types ofdevices.

FIG. 6B shows one contemplated multi-chambered fabrication apparatus 621that can be used to apply techniques disclosed herein. Generallyspeaking, the depicted apparatus 621 includes several general modules orsubsystems including a transfer module 623, a printing module 625 and aprocessing module 627. Each module maintains a controlled environment,such that printing for example can be performed by the printing module625 in a first controlled atmosphere and other processing, for example,another deposition process such an inorganic encapsulation layerdeposition or a curing process (e.g., for printed materials), can beperformed in a second controlled atmosphere. The apparatus 621 uses oneor more mechanical handlers to move a substrate between modules withoutexposing the substrate to an uncontrolled atmosphere. Within any givenmodule, it is possible to use other substrate handling systems and/orspecific devices and control systems adapted to the processing to beperformed for that module.

Various embodiments of the transfer module 623 can include an inputloadlock 629 (i.e., a chamber that provides buffering between differentenvironments while maintaining a controlled atmosphere), a transferchamber 631 (also having a handler for transporting a substrate), and anatmospheric buffer chamber 633. Within the printing module 625, it ispossible to use other substrate handling mechanisms such as a flotationtable for stable support of a substrate during a printing process.Additionally, a xyz-motion system, such as a split axis or gantry motionsystem, can be used for precise positioning of at least one printheadrelative to the substrate, as well as providing a y-axis conveyancesystem for the transport of the substrate through the printing module625. It is also possible within the printing chamber to use multipleinks for printing, e.g., using respective printhead assemblies suchthat, for example, two different types of deposition processes can beperformed within the printing module in a controlled atmosphere. Theprinting module 625 can comprise a gas enclosure 635 housing an inkjetprinting system, with means for introducing an inert atmosphere (e.g.,nitrogen) and otherwise controlling the atmosphere for environmentalregulation (e.g., temperature and pressure), gas constituency andparticulate presence.

Various embodiments of a processing module 627 can include, for example,a transfer chamber 636; this transfer chamber also has a including ahandler for transporting a substrate. In addition, the processing modulecan also include an output loadlock 637, a nitrogen stack buffer 639,and a curing chamber 641. In some applications, the curing chamber canbe used to cure, bake or dry a monomer film into a uniform polymer film;for example, two specifically contemplated processes include a heatingprocess and a UV radiation cure process.

In one application, the apparatus 621 is adapted for bulk production ofliquid crystal display screens or OLED display screens, for example, thefabrication of an array of (e.g.) eight screens at once on a singlelarge substrate. These screens can be used for televisions and asdisplay screens for other forms of electronic devices. In a secondapplication, the apparatus can be used for bulk production of solarpanels in much the same manner.

The printing module 625 can advantageously be used in such applicationsto deposit organic light generating layers or encapsulation layers thathelp protect the sensitive elements of OLED display devices. Forexample, the depicted apparatus 621 can be loaded with a substrate andcan be controlled to move the substrate back and forth between thevarious chambers in a manner uninterrupted by exposure to anuncontrolled atmosphere during the encapsulation process. The substratecan be loaded via the input loadlock 629. A handler positioned in thetransfer module 623 can move the substrate from the input loadlock 629to the printing module 625 and, following completion of a printingprocess, can move the substrate to the processing module 627 for cure.By repeated deposition of subsequent layers, each of controlledthickness, aggregate encapsulation can be built up to suit any desiredapplication. Note once again that the techniques described above are notlimited to encapsulation processes, and also that many different typesof tools can be used. For example, the configuration of the apparatus621 can be varied to place the various modules 623, 625 and 627 indifferent juxtaposition; also, additional, fewer or different modulescan also be used.

While FIG. 6B provides one example of a set of linked chambers orfabrication components, clearly many other possibilities exist. Thetechniques introduced above can be used with the device depicted in FIG.6B, or indeed, to control a fabrication process performed by any othertype of deposition equipment.

FIG. 6C provides a plan view of the substrate and printer as they mightappear during the deposition process. The print chamber is generallydesignated by reference numeral 651, the substrate to be printed upon isgenerally designated by numeral 653, and a support table used totransport the substrate is generally designated by numeral 655.Generally speaking, any xy coordinate of the substrate is reached by acombination of movements, including x- and y-dimensional movement of thesubstrate by the support table (e.g., using flotation support, asdenoted by numeral 657) and using “slow axis” x-dimensional movement ofone or more printheads 659 along a traveler 661, as generallyrepresented by arrows 663. As mentioned, the flotation table andsubstrate handling infrastructure are used to move the substrate andadvantageously provide deskew control along one or more “fast axes,” asnecessary. The printhead is seen to have plural nozzles 665, each ofwhich is separately controlled by a firing pattern derived from atemplate (e.g., to effectuate printing of columns corresponding toprinter grid points as the printhead is moved from left-to-right andvice-versa along the “slow axis”). With relative motion between the oneor more printheads and the substrate provided in the direction of thefast axis (i.e., the y-axis), printing describes a swath that typicallyfollows individual rows printer grid points. The printhead can alsoadvantageously be adjusted to vary effective nozzle spacing (e.g., byrotating of the one or more printheads, per numeral 667). Note thatmultiple such printheads can be used together, oriented withx-dimension, y-dimension, and/or z-dimensional offset relative to oneanother as desired (see axis legend 669 in FIG. 6C). The printingoperation continues until the entire target region (and any borderregion) has been printed with ink, as desired. Following deposition ofthe necessary amount of ink, the substrate is finished, either byevaporating solvent to dry ink (e.g., using a thermal process), or byuse of a cure process, such as a UV cure process.

FIG. 6D provides a block diagram showing various subsystems of oneapparatus (671) that can be used to fabricate devices having one or morelayers as specified herein. Coordination over the various subsystems isprovided by a set of processors 673, acting under instructions providedby software (not shown in FIG. 6D). As noted earlier, to performon-the-fly transformations to correct for substrate or panel error, inone embodiment, these processors include a supervisory processor orgeneral purpose CPU, and a set of additional processors used forparallel processing. In one specifically-contemplated implementation,these additional processors take the form of a multicore processor orgraphics processing unit (GPU, e.g., with hundreds of cores, or more).Each core is assigned a portion of the print image to transform todistort the print image to match substrate error; if error is to beindependently corrected on a panel or other product-by-product basis,then the each core can advantageously be assigned to a fraction orportion of a single product or panel (i.e., such that the specific coreperforms only a single transform operation on all assigned image data).Parallel processing and/or this form of delegation are not required forall embodiments. During a fabrication process, the processors feed datato a printhead 675 to cause the printhead to eject various volume of inkdepending on firing instructions provided by a halftone print image. Theprinthead 675 typically has multiple ink jet nozzles, arranged in a rowor array, and associated reservoirs that permit jetting of inkresponsive to activation of piezoelectric or other transducers; suchtransducers cause a respective nozzle to eject a controlled amount ofink in an amount governed by an electronic firing waveform signalapplied to the corresponding piezoelectric transducer. Other firingmechanisms can also be used. The printhead applies the ink to asubstrate 677 at various x-y positions corresponding to the gridcoordinates, as represented by the halftone print image. Variation inposition is effected both by a printhead motion system 679 and substratehandling system 681 (e.g., that cause the printing to describe one ormore swaths across the substrate). In one embodiment, the printheadmotion system 679 moves the printhead back-and-forth along a traveler,while the substrate handling system provides stable substrate supportand both “x” and “y” dimension transport (and rotation) of thesubstrate, e.g., for alignment and deskew; during printing, thesubstrate handling system provides relatively fast transport in onedimension (e.g., the “y” dimension relative to FIG. 6C), while theprinthead motion system 679 provides relatively slow transport inanother dimension (e.g., the “x” dimension relative to FIG. 6C), e.g.,for printhead offset. In another embodiment, multiple printheads can beused, with primary transport being handled by the substrate handlingsystem 681. An image capture device 683 can be used to locate anyfiducials and assist with alignment and/or error detection functionsdescribed earlier.

The apparatus also comprises an ink delivery system 685 and a printheadmaintenance system 687 to assist with the printing operation. Theprinthead can be periodically calibrated or subjected to a maintenanceprocess; to this end, during a maintenance sequence, the printheadmaintenance system 687 is used to perform appropriate priming, purge ofink or gas, testing and calibration, and other operations, asappropriate to the particular process. Such a process can also includeindividual measurement of parameters such as droplet volume, velocityand trajectory, for example, as discussed in Applicant's PCT patentapplication referenced earlier (PCT/US14/35193), and as referenced bynumerals 691 and 692.

As was introduced previously, the printing process can be performed in acontrolled environment, that is, in a manner that presents a reducedrisk of contaminants that might degrade effectiveness of a depositedlayer. To this effect, the apparatus includes a chamber controlsubsystem 689 that controls atmosphere within the chamber, as denoted byfunction block 690. Optional process variations, as mentioned, caninclude performing jetting of deposition material in presence of anambient nitrogen gas atmosphere (or another inert environment, having aspecifically selected gas and/or controlled to exclude unwantedparticulate). Finally, as denoted by numeral 693, the apparatus alsoincludes a memory subsystem that can be used to store halftone patterninformation or halftone pattern generation software, template printimage data, and other data as necessary. For example, the memorysubsystem can be used as operating memory for the transformation of apreviously generated print image according to the techniques introducedabove, to internally generate printer control instructions that governthe firing of (and timing of) each droplet. If part or all of suchrendering is performed elsewhere, and the task of the apparatus is tofabricate a device layer according to a received printer instructions,then the received instructions can be stored in the memory subsystem 693for use during the printing process and/or manipulation as appropriate.As noted by numeral 694, in one optional embodiment, individual dropletparticulars can be varied (e.g., to correct for nozzle aberration)through the variation of firing waveform for any given nozzle. In oneembodiment, a set of alternate firing waveforms can be selected inadvance and made available to each nozzle, on a shared or dedicatedbasis, optionally used in conjunction with substrate variation (error)processing 695, as described earlier. As noted, while some embodimentsuse predetermined scan paths (i.e., notwithstanding error), withcompensation for error effectuated using different nozzles and/or drivewaveforms for certain nozzles, in another embodiment, print optimization(696) is performed to reassess scan path particulars and potentiallyimprove on deposition time.

FIG. 7 provides another flow diagram 701 associated with some of thediscussed processes. As with the earlier examples, data representinglayout of a desired layer is first received, per numeral 703. This dataspecifies boundaries of the layer to be deposited and providesinformation sufficient to define thicknesses throughout the layer ofinterest (e.g., for a given panel). This data can be generated on thesame machine or device on which the process 701 is performed, or it canbe generated by a different machine. In one embodiment, the receiveddata is defined according to an xy coordinate system and the providedinformation is sufficient to compute desired layer thickness at anyrepresented xy coordinate point, for example, optionally specifying asingle height or thickness to be applied throughout the layer,consistent with the x-micron by y-micron by z-micron example introducedearlier. Per numeral 705, this data can be converted to a grayscalevalue for each print cell (or each print pixel) in a deposition areathat will receive the layer. If print cell area does not inherentlycorrespond to the xy coordinate system matching the layout data, thenthe layout data is converted (e.g., by averaging thickness data formultiple coordinate points and/or using interpolation) to obtain agrayscale value for each print pixel. This conversion can be based onpredetermined mapping information, for example, produced usingrelationships or equations. Per numeral 707, grayscale values canoptionally be adjusted in order to produce a homogeneous layer (or forother desired effect). To provide one example, if it is desired tocompensate for varying heights of microstructures that will situnderneath the desired layer, an optional technique adds offsets toselect grayscale values to “boost” the layer of interest at specificlocations to effectively planarize a top surface of the deposited layer.In one embodiment, grayscale value manipulation can also be used tocorrect for nozzle firing aberration (e.g., in the in-scan direction) todeposit more ink (for example, if a particular nozzle or set of nozzlesproduce insufficient ink volume) or less ink (e.g., the particularnozzle or set of nozzles produce excess ink volume). Such an optionalprocess can be predicated on a calibration process and/orempirically-determined data, per function block 714. The grayscalevalues are then converted to a droplet density pattern (e.g., a specifichalftone pattern), per numeral 709, and a bitmap is then generated, pernumeral 710. Error diffusion, as indicated by the FIG., can be reliedupon to help promote layer homogeneity.

FIG. 7 shows use of a collection of a number of nozzle/waveform errorcorrection processes 713, optionally applied to help ensure uniformityand accuracy in the deposited layer and adjust for detected panel orsubstrate positional errors. Such uniformity can be important to devicequality, whether to ensure accurate registration with any underlyingproduct layers, development of adequate encapsulation to produce awater/oxygen barrier, or to provide high-quality light generating orlight guiding elements of a display panel, or for other purpose oreffect. As noted above, a calibration process or empirically determined(dead-reckoned) data can be used to correct for errors in grayscalevalue, or for nozzle or nozzle-waveform particulars, or for substrate orpanel positional variation, per numeral 714. Alternatively, individualnozzle drive waveforms can be planned or adjusted to correct error, asrepresented by numeral 715. In another embodiment, as noted earlier,nozzles can be validated or qualified (719), with each nozzle eitherdetermined to meet minimum droplet generation thresholds or disqualifiedfrom use. If a specific nozzle has been disqualified but is tentativelyselected for use, then in order to provide for appropriate dropletdeposition, a different nozzle (or repeated pass of acceptable nozzles)can be used to deposit the droplet(s) that would otherwise have beenprinted by the disqualified nozzle, per numeral 716. For example, in oneembodiment, a printhead has nozzles arranged both in rows and columns,such that if one nozzle is aberrant, a different, redundant nozzle canbe used to deposit the droplet desired for a particular grid point.Optionally also, such issues can be taken into account and used toadjust a scan path, for example, offsetting the printhead in a mannersuch that the desired droplet(s) can be deposited using a differentnozzle (with the printhead adjusted in position so as to permit this),or increasing or decreasing the number of scans. This is represented bythe numeral 717 in FIG. 7. Many such alternatives are possible. Asrepresented by numerals 720 and 721, in one embodiment, each nozzle iscalibrated in advance using a droplet measurement device (720) thatrepeatedly measures droplet parameters (to develop a per-nozzle orper-drive waveform distribution of measurements), with software thenbuilding a statistical model (721) for each nozzle with an understandingof nozzle positional error and/or nozzle droplet means for volume,velocity and trajectory, and with an understanding of expectedper-nozzle variance for each of these parameters. This data can be usedto qualify/validate specific nozzles (and/or droplets), as mentioned, orto select nozzles that will be used to produce each individual droplet,and to otherwise adjust or customize a template print image for each newsubstrate or other product array. Each such measurement/error correctionprocess can be factored into print planning (722), including print imageadjustment/customization, and to any scan path planning and/or printgrid computation, i.e., such that printer control data is generatedand/or updated so as to optimize the print process, while ensuringdesired layer properties. Finally, per numeral 725, final print data isthen generated for sending to the printer at run time.

FIGS. 8A-8D are used to generally introduce techniques for per-nozzledroplet measurement and validation.

More particularly, FIG. 8A provides an illustrative view depicting anoptics system 801 and a relatively large printhead assembly 803 (i.e.,represented by nozzle plates of respective printheads 805A/805B, eachwith a multitude of individual nozzles, e.g., 807); in a typicalimplementation, hundreds-to-thousands of nozzles are present. An inksupply (not shown) is fluidically connected with each nozzle (e.g.,nozzle 807), and a piezoelectric transducer (also not shown) is used tojet droplets of ink under the control of a per-nozzle electric controlsignal. The nozzle design maintains slightly negative pressure of ink ateach nozzle (e.g., nozzle 807) to avoid flooding of the nozzle plate,with the electric signal for a given nozzle being used to activate thecorresponding piezoelectric transducer, pressurize ink for the givennozzle, and thereby expel one or more droplets from the given nozzle. Inone embodiment, the control signal for each nozzle is normally at zerovolts, with a positive pulse or signal level at a given voltage used fora specific nozzle to eject droplets (one per pulse) for that nozzle; inanother embodiment, different, tailored pulses (or other, more complexwaveforms) can be used nozzle-to-nozzle. In connection with the exampleprovided by FIG. 8A, however, it should be assumed that it is desired tomeasure a droplet volume produced by a specific nozzle (e.g., nozzle807) where a droplet is ejected downward from the printhead (i.e., inthe direction “h,” representing z-axis height relative to athree-dimensional coordinate system 808) to be collected by a spittoon809. Note that in a typical application, the dimension of “h” istypically on the order of one millimeter or less and that there arethousands of nozzles (e.g., 10,000 nozzles) that are to have respectivedroplets individually measured in this manner within an operatingprinter. Thus, in order to optically measure each droplet with precision(i.e., droplets originating from a specific one of thousands of nozzlesin a large printhead assembly environment, within the approximatelymillimeter measurement window, as just described), certain techniquesare used in disclosed embodiments to precisely position elements of theoptics assembly 801, the printhead assembly 803, or both relative to oneanother for optical measurement.

In one embodiment, these techniques utilize a combination of (a) x-ymotion control (811A) of at least part of the optical system (e.g.,within dimensional plane 813) to precisely position a measurement area815 immediately adjacent to any nozzle that is to produce a droplet foroptical calibration/measurement and (b) below plane optical recovery(811B) (e.g., thereby permitting easy placement of the measurement areanext to any nozzle notwithstanding a large printhead surface area).Thus, in an exemplary environment having about 10,000 or more printnozzles, this motion system is capable of positioning at least part ofthe optical system in (e.g.) 10,000 or so discrete positions proximateto the discharge path of each respective nozzle of the printheadassembly; in one embodiment, a continuous motion system or a systemhaving even finer positioning capabilities can be used. As will bediscussed below, two contemplated optical measurement techniques includeshadowgraphy and interferometry. With each, optics are typicallyadjusted in position so that precise focus is maintained on themeasurement area so as to capture droplets in-flight (e.g., toeffectively image the droplet's shadow in the case of shadowgraphy).Note that a typical droplet may be on the order of microns in diameter,so the optical placement is typically fairly precise, and presentschallenges in terms of relative positioning of the printhead assemblyand measurement optics/measurement area. In some embodiments, to assistwith this positioning, optics (mirrors, prisms, and so forth) are usedto orient a light capture path for sensing below the dimensional plane813 originating from the measurement area 815, such that measurementoptics can be placed close to the measurement area without interferingwith relative positioning of the optics system and printhead. Thispermits effective positional control in a manner that is not restrictedby the millimeter-order deposition height h within which a droplet isimaged or the large scale x and y width occupied by a printhead underscrutiny. With interferometry-based droplet measurement techniques,separate light beams incident from different angles on a small dropletcreates interference patterns detectable from a perspective generallyorthogonal to the light paths; thus, optics in such a system capturelight from an angle of approximately ninety-degrees off of paths of thesource beams, but also in a manner that utilizes below plane opticalrecovery so as to measure droplet parameters. Other optical measurementtechniques can also be used. In yet another variant of these systems,the motion system 811A is optionally and advantageously made to be anxyz-motion system, which permits selective engagement and disengagementof the droplet measurement system without moving the printhead assemblyduring droplet measurement. Briefly introduced, it is contemplated in anindustrial fabrication device having one or more large printheadassemblies that, to maximize manufacturing uptime, each printheadassembly will be “parked” in a service station from time to time toperform one or more maintenance functions; given the sheer size of theprinthead and number of nozzles, it can be desired to perform multiplemaintenance functions at once on different parts of the printhead. Tothis effect, in such an embodiment, it can be advantageous to movemeasurement/calibration devices around the printhead, rather thanvice-versa. [This then permits engagement of other non-opticalmaintenance processes as well, e.g., relating to another nozzle ifdesired.] To facilitate these actions, the printhead assembly can beoptionally “parked,” with the system identifying a specific nozzle orrange of nozzles that are to be the subject of optical calibration. Oncethe printhead assembly or a given printhead is stationary, the motionsystem 811A is engaged to move at least part of the optics systemrelative to the “parked” printhead assembly, to precisely position themeasurement area 815 at a position suitable for detecting a dropletjetted from a specific nozzle; the use of a z-axis of movement permitsselective engagement of light recovery optics from well below the planeof the printhead, facilitating other maintenance operations in lieu ofor in addition to optical calibration. Perhaps otherwise stated, the useof an xyz-motion system permits selective engagement of a dropletmeasurement system independent of other tests or test devices used in aservice station environment. Note that this structure is not requiredfor all embodiments; other alternatives are also possible, such in whichonly the printhead assembly moves and the measurement assembly isstationary or in which no parking of the printhead assembly isnecessary.

Generally speaking, the optics used for droplet measurement will includea light source 817, an optional set of light delivery optics 819 (whichdirect light from the light source 817 to the measurement area 815 asnecessary), one or more light sensors 821, and a set of recovery optics823 that direct light used to measure the droplet(s) from themeasurement area 815 to the one or more light sensors 821. The motionsystem 811A optionally moves any one or more of these elements togetherwith spittoon 809 in a manner that permits the direction of post-dropletmeasurement light from the measurement area 815 around spittoon 809 to abelow-plane location, while also providing a receptacle (e.g., spittoon809) to collect jetted ink. In one embodiment, the light delivery optics819 and/or the light recovery optics 823 use mirrors that direct lightto/from measurement area 815 along a vertical dimension parallel todroplet travel, with the motion system moving each of elements 817, 819,821, 823 and spittoon 809 as an integral unit during dropletmeasurement; this setup presents an advantage that focus need not berecalibrated relative to measurement area 815. As noted by numeral 811C,the light delivery optics are also used to optionally supply sourcelight from a location below the dimensional plane 813 of the measurementarea, e.g., with both light source 817 and light sensor(s) 821 directinglight on either side of spittoon 809 for purposes of measurement, asgenerally illustrated. As noted by numerals 825 and 827, the opticssystem can optionally include lenses for purposes of focus, as well asphotodetectors (e.g., for non-imaging techniques that do not rely onprocessing of a many-pixeled “picture”). Note once again that theoptional use of z-motion control over the optics assembly and spittoonpermits optional engagement and disengagement of the optics system, andprecise positioning of measurement area 815 proximate to any nozzle, atany point in time while the printhead assembly is “parked.” Such parkingof the printhead assembly 803 and xyz-motion of the optics system 801 isnot required for all embodiments. For example, in one embodiment, laserinterferometry is used to measure droplet characteristics, with eitherthe printhead assembly (and/or the optics system) is moved within orparallel to the deposition plane (e.g., within or parallel to plane 813)to image droplets from various nozzles; other combinations andpermutations are also possible.

FIG. 8B provides flow of a process associated with droplet measurementfor some embodiments. This process flow is generally designated usingnumeral 831 in FIG. 8B. More specifically, as indicated by referencenumeral 833, in this particular process, the printhead assembly is firstparked, for example, in a service station (not shown) of a printer ordeposition apparatus. A droplet measurement device is then engaged (835)with the printhead assembly, for example, by selective engagement ofpart or all of an optics system through movement from below a depositionplane into a position where the optics system is capable of measuringindividual droplets. Per numeral 837, this motion of one or moreoptics-system components relative to a parked printhead can optionallybe performed in x, y and z dimensions.

As alluded to previously, even a single nozzle and associated nozzlefiring drive waveform (i.e., pulse(s) or signal level(s) used to jet adroplet) can produce droplet volume, trajectory, and velocity thatvaries slightly from droplet to droplet. In accordance with teachingsherein, in one embodiment, the droplet measurement system, as indicatedby numeral 839, obtains n measurements per droplet of a desiredparameter, to derive statistical confidence regarding the expectedproperties of that parameter. In one implementation, the measuredparameter can be volume, whereas for other implementations, the measuredparameter can be flight velocity, flight trajectory, nozzle positionerror (e.g., nozzle bow) or another parameter, or a combination ofmultiple such parameters. In one implementation, “n” can vary for eachnozzle, whereas in another implementation, “n” can be a fixed number ofmeasurements (e.g., “24”) to be performed for each nozzle; in stillanother implementation, “n” refers to a minimum number of measurements,such that additional measurements can be performed to dynamically adjustmeasured statistical properties of the parameter or to refineconfidence. Clearly, many variations are possible. For the exampleprovided by FIG. 8B, it should be assumed that droplet volume is beingmeasured, so as to obtain an accurate mean representing expected dropletvolume from a given nozzle and a tight confidence interval. This meancan be assigned by a processor in view of pertinent measurement data,weighted or otherwise. This enables optional planning of dropletcombinations (using multiple nozzles and/or drive waveforms) whilereliably maintaining distributions of composite ink fills in a targetregion about an expected target (i.e., relative to a composite ofdroplet means). As noted by optional process boxes 841 and 843,interferometry or shadowgraphy are contemplated optical measurementprocesses that ideally enable instantaneous or near instantaneousmeasurement and calculation of volume (or other desired parameter); withsuch fast-measurement, it becomes possible to frequently and dynamicallyupdate volume measurements, for example, to account for changes overtime in ink properties (including viscosity and constituent materials),temperature, power supply fluctuation and other factors. Building onthis point, shadowgraphy typically features capture of an image of adroplet, for example, using a high resolution CMOS or CCD camera as alight sensor mechanism; while droplets can be accurately imaged in asingle image capture frame at multiple positions (e.g., using a strobedlight source), image acquisition typically involves a finite amount oftime, such that imaging of a sufficient droplet population from a largeprinthead assembly (e.g., with thousands of nozzles) can take hours.Interferometry, which relies on multiple binary light detectors anddetection of interference pattern spacing based on output of suchdetectors, is a non-imaging technique (i.e., that does not require imageanalysis) and so produces droplet volume measurements many orders oftime faster (e.g., 50×) than shadowgraphy or other techniques; forexample, with a 10,000 nozzle printhead assembly, it is expected thatlarge measurement populations for each of the thousands of nozzles canbe obtained in minutes, rendering it feasible to frequently anddynamically perform droplet measurement. As noted earlier, in oneoptional embodiment, droplet measurement (or measurement of otherparameters, such as trajectory and/or velocity) can be performed as aperiodic, intermittent process, with the droplet measurement systembeing engaged according to a schedule, or in between substrates (e.g.,as substrates are being loaded or unloaded), or stacked against otherassembly and/or other printhead maintenance processes. Note that forembodiments that permit alternate nozzle drive waveforms to be used in amanner specific to each nozzle, a rapid measurement system (e.g.,interferometric system) readily permits statistical populationdevelopment for each nozzle and for each alternative drive waveform forthat nozzle, thereby facilitating planned droplet combinations ofdroplets produced by various nozzle-waveform pairings, as alluded toearlier. Per numerals 845 and 847, by measuring expected droplet volumenozzle-by-nozzle (and/or by nozzle-waveform pairing-by-pairing) to aprecision of better than 0.01 pL, it becomes possible to plan for veryprecise droplet combinations per target deposition region, wherecomposite fills can also be planned to 0.01 pL resolution, and wheretarget volumes can be kept within a specified error (e.g., tolerance)range of 0.5% of target volume or better; as indicated by numeral 847,the measurement populations for each nozzle or each nozzle-waveformpairing are in one embodiment planned so as to produce reliabilitydistribution models for each such nozzle or nozzle-waveform pairing,i.e., with 36 confidence (or other statistical measure, such as 46, 56,66, etc.) relative to allowable droplet tolerance. Once sufficientmeasurements are taken for various droplets, fills involvingcombinations of those droplets can be evaluated and used to planprinting (848) in the most efficient manner possible. As indicated byseparation line 849, droplet measurement can be performed withintermittent switching back and forth between active printing processesand measurement and calibration processes; note that to minimizemanufacturing system downtime, such measurement is typically performedwhile the printer is tasked with other processes, e.g., during substrateloading and unloading.

FIG. 8C illustrates another embodiment of a method of dropletmeasurement, generally represented by numeral 851. When a printhead ismounted or it is otherwise desired to calibrate the droplet measurementsystem to correct for positional offset, a calibration routine can berun in order to precisely match droplet measurements with a givenprinthead nozzle. In a typical embodiment, this alignment process isperformed with the aid of an “upward facing camera” or other imagingdevice that takes an image of a printhead from beneath, that is, lookingupward from the perspective of a substrate at the nozzle plate toidentify one or more printhead fiducials or alignment marks (853). Inone embodiment, the camera (imaging system) can be the same device asused for droplet measurement, but it can also be a separate imagingdevice. For an exemplary printhead having, e.g., 1024 nozzles arrangedin four rows of 256 nozzles, fiducials on the nozzle plate (not to beconfused with substrate fiducials) are used to determine offset androtational skew between the nozzle plate and a grid system correspondingto the imaging device. Note that in one embodiment, the fiducials canoptionally be specific nozzles (854), for example, the nozzles closestto the corners of the printhead (e.g., first and fourth rows, nozzles 1and 256); other mechanisms can also be used. In a typicalimplementation, printhead configuration data (855) is loaded into thesystem by software and used to identify these corner nozzles and used tomap address of all nozzles to the imaging system's grid 856, withinterpolation relied upon to initially estimate position of each nozzle(857). To provide an example, in one embodiment, system software isdesigned to accommodate different printheads with different nozzleconfigurations, and to this effect, the system software loads theprinthead configuration data to identify number of rows, presence offiducials (if any), number of nozzles per-row, average vertical andhorizontal offset between rows and columns of nozzles, and so forth.This data enables the system software to estimate the position of eachnozzle on the printhead, as mentioned. In one contemplated system, thiscalibration process is performed once a printhead is changed, but not inbetween print processes; in a different embodiment, this calibrationprocess is performed each time the droplet measurement system isinitialized, e.g., with each new measurement run in between two printoperations.

During production, nozzle (and nozzle-waveform) measurement can beperformed on a rolling basis, precessing through a range of nozzles witheach break in between substrate print operations. Whether engaged tomeasure all nozzles anew, or on such a rolling basis, the same basicprocess of FIG. 8C can be employed for measurement. To this effect, pernumerals 858 and 859, when the droplet measurement device is engaged fora new measurement (either on the heels of prior measurement or asubstrate print operation), the system software can identify identifiesthe next nozzle for which measurements are to be taken (e.g., by loadinga pointer to “nozzle 2,312” for the “312^(th)” nozzle of a secondprinthead). In the case of initial measurement (e.g., responsive toinstallation of a new printhead, or a recent boot-up, or a periodicprocess such as a daily measurement process), the pointer would point toa first nozzle for a printhead, e.g., “nozzle 2,001.” This nozzle eitheris associated with a specific imaging grid access or one is looked-upfrom memory. The system uses the provided address to advance the dropletmeasurement system (e.g., the spittoon and measurement area referencedearlier) to a position corresponding to the expected nozzle position.Note that in a typical system, the mechanical throws associated withthis movement are quite precise, i.e., to approximately micronresolution. The system optionally at this time searches for nozzleposition about the expected micron-resolution position, and finds thenozzle and centers on its position (860) based on image analysis of theprinthead within a small micron-distance from the estimated gridposition. For example, a zig-zag, spiral or other search pattern can beused to search about the expected position for a nozzle. [Note that inone embodiment, this process can also be manually performed byadjustment of the printer by a human operator.] A typical pitch distancebetween nozzles might be on the order of 250 microns, whereas nozzlediameter might be on the order of 10-20 microns. Once the nozzle ofinterest is identified, the software fires a droplet from the nozzle inquestion and relies on the droplet measurement system to confirm thatthe nozzle in-question did indeed fire (which then confirms the nozzle'sidentity). FIG. 8C shows this process as being performed every time anew nozzle is identified for measurement (e.g., every time the dropletmeasurement system moves), but it is also possible in some embodimentsto perform this measurement once (e.g., in situations where the dropletmeasurement system grid is very tight) during an off-line configuration,to store the grid position for each nozzle, and then to update thisposition only when the printhead is changed or in response to errorprocessing. In systems where the mechanics of the droplet measurementsystem and/or printhead position are not very precise, it can beadvantageous to use an estimate and search function for each nozzleanytime there is a change in the nozzle under scrutiny. Note that asimplied by numeral 861, in one embodiment, the estimate and searchfunction aligns the droplet measurement device (and its associatedoptics) in each of three dimensions (xyz) with the printhead nozzleunder scrutiny.

The precise z position of each nozzle (distance relative to dropletmeasurement area) is then adjusted (862) in order to ensure consistentdroplet measurement and/or image capture. For example, it was mentionedearlier that a droplet measurement system typically determines dropletvelocity and flight trajectory by measuring each droplet multiple times,and calculating these parameters based on distance (e.g., relative to acentroid of each droplet image). Various parameters can affect properdroplet measurement, including error in strobe timing (e.g., for ashadowgraphy-based droplet measurement system), uncorrected alignmenterrors between the droplet imaging system and the nozzle plate, nozzleprocess corners and other factors. In one embodiment, a variety ofstatistical processes are used to compensate for such errors, forexample, in a manner that normalizes strobe firing relative to dropletmeasurement locations across all droplets; for example, if ahypothetical printhead has 1,000 nozzles, then the system can normalizez-axis offset from the printhead plate by picking an average offsetwhich produces a minimum of positional error while centering a desirednumber of droplets (on average across the 1,000 nozzles or subsetsthereof) in the measurement area, in terms of average droplet imageposition. Analogous techniques can be applied to an interferometry-basedsystem or to other droplet measurement systems.

FIG. 8C shows a droplet measurement area 863 and a hypothetical passageof two droplets 864 and 866 through that measurement area, alongrespective hypothetical trajectories 865 and 867. Several things shouldbe noted about the example provided by this FIG. First, velocity andtrajectory measurement is seen to be dependent on measuring the samedroplet multiple times (three each in the case of droplets 864 and 866).This requirement can be used to properly position the measurement arearelative to the strobe (or imaging source) firing, by one or more ofchanging the timing of the strobe (or light source), changing the drivewaveform used to launch the associated droplets, changing z-axisposition of the droplet measurement system, and/or changing z-axisposition of the printhead. For example, if three droplet images areexpected for a single droplet as the strobe is repeatedly fired (duringa single exposure, in the case of a shadowgraphy-based system), but onlytwo are observed, the measurement area is misaligned in height, and isadjusted to effectively redefine where droplet positions are capturedrelative to the measurement area until three exposures are obtained.Naturally, this hypothetical provides an example only and otherimplementations might measure more than 3 strobed droplet exposures orless than 3 exposures. Note also deviation in trajectory 865 relative totrajectory 867 might be due to statistical variation in the way thedroplets are produced, and so can be optionally used to build astatistical model representing mean droplet trajectory (in terms ofalpha and beta angle) and standard deviation in each of thesedimensions. As should be appreciated, while droplet measurement areas863 shows a two-dimensional droplet depiction (e.g., a yz plane as perthe drawing page), trajectory angle relative to the x axis can bederived from changes in apparent droplet size in a given image frameamongst the multiple strobed exposures, indicating that droplet isgetting nearer or farther away from the plane of the drawing sheetrepresented by FIG. 8C; analogous interference pattern changes areapplied in the case of interferometry-based techniques.

The scheme represented within measurement 863 can also be used tomeasure nozzle row bow. That is, as an example, if it is assumed thatdroplets 864 and 866 originate from a common exact nozzle position, butthe reverse trajectory does not align with the expected y-axis center ofthe droplet measurement area (i.e., from the left-to-right relative tothe drawing page) that the nozzle in question could be offset in itsy-axis position relative to other nozzles in the same row or column. Asimplied by the discussion earlier, such aberration can lead to idealizeddroplet firing deviations that can be taken into account in planningprecise combinations of droplets, i.e., preferably, any such row “bow”or individual nozzle offset is stored and used as part of print scanplanning, as discussed earlier, with the printing system using thedifferences of each individual nozzle in a planned manner rather thanaveraging out those differences. In an optional variation, the sametechnique can be used to determine non-regular nozzle spacing along thex-axis, although for the depicted embodiment, any such error is subsumedin correction for droplet velocity deviations (e.g., any such spacingerror can be corrected for by adjustments to nozzle velocity). Todetermine y-axis bow of a nozzle producing droplets 864 and 866, therespective trajectories 865 and 867 are effectively reverse plotted (orotherwise mathematically applied) with other measurement trajectoriesfor the same nozzle and used to identify a mean y-axis position of thespecific nozzle under scrutiny. This position may be offset from anexpected location for such a nozzle, which could be evidence of nozzlerow bow.

As stated before and as implied by this discussion, one embodimentbuilds a statistical distribution for each nozzle for each parameterbeing measured, for example, for volume, velocity, trajectory, nozzlebow, and potentially other parameters (868). As part of thesestatistical processes, individual measurements can be thrown out or usedto identify errors. To cite a few examples, if a droplet measurement isobtained having a value that is so far removed from other measurementsof the same nozzle that the measurement could represent a firing error;in one implementation, the system discards this measurement if deviantto a point that exceeds a statistical error parameter. If no droplet isseen at all, this could be evidence that the droplet measurement systemis at the wrong nozzle (wrong position), or has a firing waveform erroror that a nozzle under scrutiny is inoperative. Measurement errorhandling process 869 is employed to make appropriate adjustmentsincluding taking any new or additional measurements as necessary. Pernumeral 870, each measurement is advantageously stored and used to buildthe pertinent statistical distributions, with the system then looping toperform measurement for additional droplets from the same nozzle untilsufficient robustness to measurement error is obtained. This loop (871)is seen in FIG. 8C to indicate performance until n droplets are obtainedfor each nozzle or each nozzle-waveform pairing. When a sufficientlyrobust distribution has been obtained, the system calculates (stores)and assigns the desired statistical parameter(s) (e.g., mean, standarddistribution for each measure parameter) to the given nozzle (872) andexecutes any appropriate error handling process 873 (such as validatingthe nozzle just measured or deeming it or an associated waveforminoperative) and then moves on to the next firing waveform or nextnozzle (874), as appropriate. That is, with a measurement distributionfor a given nozzle or nozzle-waveform pairing having been completed, thesystem software can identify the next nozzle to be measured (874, e.g.,by updated an address pointer) and then returns per numeral 876 to movethe droplet measurement system and to perform the next measurement, asappropriate. Alternatively, per numeral 875, if time is up, and thesystem is being called upon to print another substrate as part of amanufacturing line, the system updates any scanning operations based onnewly procured data (if any), stores the “next” nozzle's address, andreturns to substrate printing (875). In one embodiment, after such aprinting operation is complete, during a prospective break (ormaintenance downtime), the system retrieves the stored nozzle addressand particulars of droplet measurement and continues where it left off.

Note that, although not separately called out by FIG. 8C, the depictedmeasurement process would typically be performed for each alternatewaveform available for use with each nozzle. For example, if each nozzlehad four different piezoelectric drive waveforms that could be selected,the inner process loop 871 of FIG. 8C would generally be repeated 4*ntimes; if a particular implementation called for the building of astatistical distribution based on 24 droplets for each waveform, thenthere might be 96 such measurements for one nozzle (24 for each of fourwaveforms), with each measurement being used to develop statistical meanand spread measures for each of droplet velocity, trajectory and volume,and for estimated nozzle position (e.g., for purposes of assessingnozzle bow).

FIG. 8D provides a flow diagram relating to nozzle qualification. In oneembodiment, droplet measurement is performed to yield statistical models(e.g., distribution and mean) for each nozzle and for each waveformapplied to any given nozzle, for any of and/or each of droplet volume,velocity and trajectory. Thus, for example, if there are two choices ofwaveforms for each of a dozen nozzles, there are up to 24waveform-nozzle combinations or pairings; in one embodiment,measurements for each parameter (e.g. volume) are taken for each nozzleor waveform-nozzle pairing sufficient to develop a robust statisticalmodel. Note that despite planning, it is conceptually possible that agiven nozzle or nozzle-waveform pairing may yield an exceptionally widedistribution, or a mean which is sufficiently aberrant that it should bespecially treated. Such special treatment applied in one embodiment isrepresented conceptually by FIG. 8D.

More particularly, a general method is denoted using reference numeral881. Data generated by the droplet measurement device is stored inmemory 885 for later use. During the application of method 881, thisdata is recalled from memory and data for each nozzle or nozzle-waveformpairing is extracted and individually processed (883). In oneembodiment, a normal random distribution is built for each variable tobe qualified, as described by a mean, standard deviation and number ofdroplets measured (n), or using equivalent measures. Note again thatother distribution formats (e.g., Student's-T, Poisson, etc.), can beused. Measured parameters are compared to one or more ranges (887) todetermine whether the pertinent droplet can be used in practice. In oneembodiment, at least one range is applied to disqualify droplets fromuse (e.g., if the droplet has a sufficiently large or small volumerelative to desired target, then that nozzle or nozzle-waveform pairingcan be excluded from short-term use). To provide an example, if 10.00 pLdroplets are desired, then a nozzle or nozzle-waveform linked to adroplet mean more than, e.g., 1.5% away from this target (e.g., <9.85 pLor >10.15 pL) can be excluded from use. Range, standard deviation,variance, or another spread measure can also or instead be used. Forexample, if it is desired to have droplet statistical models with anarrow distribution (e.g., 3σ<1.005% of mean), then droplets withmeasurements not meeting this criteria can be excluded. It is alsopossible to use a sophisticated/complex set of criteria which considersmultiple factors. For example, an aberrant mean combined with a verynarrow spread might be okay, e.g., if spread (e.g., 3σ) away frommeasured (e.g., aberrant) mean μ is within 1.005%, then an associateddroplet can be used. For example, if it is desired to use droplets with3σ volume within 10.00 pL±0.1 pL, then a nozzle-waveform pairingproducing a 9.96 pL mean with ±0.8 pL 3σ value might be excluded, but anozzle-waveform pairing producing a 9.93 pL mean with ±0.3 pL 3σ valuemight be acceptable. Clearly many possibilities are possible accordingto any desired rejection/aberration criteria (889). Note that this sametype of processing can be applied for per-droplet flight angle andvelocity, i.e., it is expected that flight angle and velocity pernozzle-waveform pairing will exhibit statistical distribution and,depending on measurements and statistical models derived from thedroplet measurement device, some droplets can be excluded. For example,a droplet having a mean velocity or flight trajectory that is outside of5% of normal, or a variance in velocity outside of a specific targetcould hypothetically be excluded from use. Different ranges and/orevaluation criteria can be applied to each droplet parameter measuredand provided by storage 885.

Note that depending on the rejection/aberration criteria 889, droplets(and nozzle-waveform combinations) can be processed and/or treated indifferent manners. For example, a particular droplet not meeting adesired norm can be rejected (891), as mentioned. Alternatively, it ispossible to selectively perform additional measurements for the nextmeasurement iteration of the particular nozzle-waveform pairing; as anexample, if a statistical distribution is too wide, it is possible tospecially perform additional measurements for the particularnozzle-waveform pairing so as to improve tightness of a statisticaldistribution through additional measurement (e.g., variance and standarddeviation are dependent on the number of measured data points). Pernumeral 893, it is also possible to adjust a nozzle drive waveform, forexample, to use a higher or lower voltage level (e.g., to providegreater or lesser velocity or more consistent flight angle), or toreshape a waveform so as to produce an adjusted nozzle-waveform pairingthat meets specified norms. Per numeral 894, timing of the waveform canalso be adjusted (e.g., to compensate for aberrant mean velocityassociated with a particular nozzle-waveform pairing). As an example(alluded to earlier), a slow droplet can be fired at an earlier timerelative to other nozzles, and a fast droplet can be fired later in timeto compensate for faster flight time. Many such alternatives arepossible. Finally, per numeral 895, any adjusted parameters (e.g.,firing time, waveform voltage level or shape) can be stored andoptionally, if desired, the adjusted parameters can be applied toremeasure one or more associated droplets. After each nozzle-waveformpairing (modified or otherwise) is qualified (passed or rejected), themethod then proceeds to the next nozzle-waveform pairing, per numeral897. Once again, specific droplet particulars are advantageously takeninto account in deriving print grid firing instructions to ensurehomogeneity in any transformed deposition parameters (at least on alocal basis). In one embodiment, nozzle particulars are weighted intothe transform computation for each grid point. In another embodiment,print grid point firing decisions are made on a weighted basis dependenton transformed template print image overlap (as discussed above), with asecond process used to cull, redistribute or otherwise adjust firingdecisions made for grid points which correspond to an aberrant dropletor nozzle; in other words, nozzle firing decisions can be made in afirst transform process, and then a second error correction process canbe applied to take into account nozzle or droplet particulars. Otheralternatives are also possible.

Through the use of precision mechanical systems and droplet measurementsystem alignment techniques, the disclosed methodology permits very highaccuracy measurement of individual nozzle characteristics, includingmean droplet metrics for each of the mentioned parameters (e.g., volume,velocity, trajectory, nozzle position, droplet landing position, nozzlebow and other parameters). As should be appreciated, the mentionedtechniques facilitate a high degree of uniformity in manufacturingprocesses, especially OLED device manufacture processes, and thereforeenhance reliability in the finished products. By providing for controlefficiencies, particularly as to speed of droplet measurement, thestacking of such measurement against other system processes and theincorporation of alignment error correction processes, the teachingspresented above help provide for a faster, less expensive manufacturingprocess designed to provide both flexibility and precision in thefabrication process.

FIGS. 9A-9C are used to illustrate an exemplary run-time printingprocess for a product array, once again, taking the example of one ormore flat panels on a substrate.

FIG. 9A depicts a substrate 901, with a number of dashed-line boxesrepresenting individual panel products. One such product, seen in thebottom left of the FIG., is designated using reference numeral 902. Eachsubstrate (in a series of substrates) in one embodiment has a number ofalignment marks, such as represented by numeral 903. In one embodiment,two such marks 903 are used for the substrate as a whole, enablingadjustment for substrate positional offset, rotation error, and scaleerror, and in another embodiment, three or more such marks 903 are usedto facilitate adjustment for skew error. In yet another embodiment, eachpanel (such as any of the four depicted panels) is accompanied byper-panel alignment marks, such as marks 905. These alignment marks canbe used to perform independent error processing per panel or perproduct; once again, a sufficient number or density of such marks (e.g.,three or more per panel or other product) enables compensation fornon-linear errors. These marks can be in addition to or in lieu ofsubstrate fiducials 903. In yet another embodiment, alignment marks arereproduced at regular intervals without regard to panel position (e.g.,such as represented by ovals 909). Whichever scheme is used, one or morecameras 906 are used to image the alignment marks in order to detect theerrors just referenced. In one contemplated embodiment, a singlemotionless camera is used, and the transport mechanism of the printer(e.g., a handler and/or air flotation mechanism) moves the substrate toposition each alignment mark in sequence in the field of view of thesingle camera; in a different embodiment, the camera is mounted on amotion system for transport relative to the substrate. In yet anotherembodiment, as discussed below, low and high magnification images aretaken, the low magnification image to coarsely position a fiducial forhigh resolution magnification, and the high magnification image toidentify precise fiducial position according to a printer coordinatesystem. Reflecting on the earlier discussion, in one embodiment, thetransport mechanism of the printer controls motion to within about amicron of intended position; the system therefore is able to preciselytrack position in software and can compute errors relative to aprinter-based or substrate-based coordinate system.

In a typical implementation, printing will be performed to deposit agiven material layer on the entire substrate at once (i.e., with asingle print process providing a layer for multiple products). Toillustrate this, FIG. 9A shows two illustrative scans 907 and 908 of aprinthead along the long axis of the substrate; in a split axis printer,the substrate is typically moved back and forth (e.g., in the directionof the depicted arrows) with the printer advancing the printheadpositionally (i.e., in the vertical direction relative to the drawingpage) in between scans. Note that while the scan paths are depicted aslinear, this is not required in any embodiment. Also, while the scanpaths (e.g., 907 and 908) are illustrated as adjacent andmutually-exclusive in terms of covered area, this also is not requiredin any embodiment (e.g., the printhead(s) can be applied on a fractionalbasis relative to a print swath, as necessary). Finally, also note thatany given scan path typically passes over the entire printable length ofthe substrate to print a layer for multiple products in a single pass.Each pass uses nozzle firing decisions according to the print image (asdistorted or corrected), and each firing decision applies a selected,programmed waveform to produce a desired droplet volume, trajectory andvelocity. Advantageously, processors on board the printer (as introducedpreviously) perform both nozzle/droplet measurement and qualificationand update of parameters, detection of per-substrate or per-panelparticulars, correction of a template, and programming of nozzle firingdata (see, e.g., “data” and “drive waveform ID” from FIG. 5B) that willbe used in association with binary nozzle firing decisions (see e.g.,“trigger (fire)” signal from FIG. 5B). Once printing is finished, thesubstrate and wet ink (i.e., deposited liquid) can then be transportedfor curing or processing of the deposited liquid into a permanent layer.For example, returning briefly to the discussion of FIG. 6B, a substratecan have “ink” applied in a printing module 625, and then be transportedto a curing chamber 641, all without breaking the controlled atmosphere(i.e., which is advantageously used to inhibit moisture, oxygen orparticulate contamination).

FIG. 9B illustrates one alignment and detection process 911 for amanufacturing operation, again using an example of flat panel devicefabrication. Note that many alternative processes are possible and thatFIG. 9B provides an example only. The process uses a tripartite methodof operation, where the new substrate is first roughly alignedmechanically, where alignment marks are then optically measured, andfinally, where software processes correct for fine (virtual) alignment.When a new substrate is loaded, a robot first places the substrate ontoprinter lift pins, which are used to advance the substrate to a vacuumgripper. The gripper moves the substrate while it is supported by an airfloatation table and the substrate is advanced to a position where it isroughly aligned and in position for optical measurement (i.e., to locatefiducials). Note that the system is programmed for rough substrateparticulars, such that a camera control system (or other imaging device)is actuated and/or activated as necessary to image an area in whichfiducial presence is expected). First, a low magnification image iscaptured and the substrate repositioned, after which a highermagnification image is used to precisely detect fiducial position.During either stage of optical measurement, a search process (e.g.,spiral) is used to find each fiducial as appropriate. The system thenproceeds to measure a second (and/or greater order fiducial asappropriate), e.g., to help identify the precise position, orientation,skew and/or scale of the substrate as appropriate; as noted earlier,this process can also be applied on a per-panel basis or, indeed, foreach and every fiducial so as to obtain position/distortion informationat a resolution appropriate to the pertinent error correction process.Detected fiducial parameters (such as position, size, shape, rotation,skew, or associated fiducial reference points) can be compared toexpected parameters for such fiducials, to detect error. As noted, anydetected error can involve one or more of translational, rotational,scaling or skew error, or a superposition of multiple such errors. Basedon detected error, printer control data is built that corrects for anyerror so that printing will be in the “right place.” As noted at theright side of the figure, based on alignment mark determination, systemsoftware corrects for error by operation upon the template. As notedearlier, the template is retrieved, and the instance of this template isthen manipulated (rendered) as appropriate to generate nozzle firingdecisions as appropriate via the aforementioned error correction process(or another equivalent process). Printing is performed thereafter.

FIG. 9C provides an illustrative diagram used to discuss substrate errorcorrection in software. In one embodiment, generally represented bynumeral 921, data is first retrieved (923) representing the layer to beprinted, e.g., according to a substrate or panel recipe, or both. Asnoted by numeral 925, this information is typically maintained as atemplate, with a copy or “instance” of the data being retrieved, adaptedto error, sent to the printer, and then discarded (i.e., to avoid datacontamination from earlier substrate processing during process of thenext substrate). These processes are variously represented in FIG. 9C.

With a copy of the template in hand, per numeral 927, the system detectssubstrate geometry; as noted by numerals 928-932, the detection processcan be performed one time (e.g., before printing starts, or as a newsubstrate is loaded), intermittently (e.g., the printing process can beinterrupted or fiducial capture can occur for each of pluralsubdivisions of the substrate, e.g., for each panel), it can be repeatedor it can be performed on a continuous basis. As specifically noted bynumeral 931, in one embodiment, multiple, different fiducials are usedto permit detection and correction for different types of linear andnon-linear errors. Once errors have been detected, the system thencalculates a transformation, per numeral 935. For example, in oneembodiment, error is linear across the substrate, and so a simple linearequation is derived and used to render the cached template in order togenerate printer control data. In other embodiments, error can bemodeled by a quadratic or other polynomial, in a manner that isdiscontinuous (e.g., according to region), or in some other manner. In aparallel processing embodiment, a master or supervisory processor makesthis determination and then assigns processing to discrete cores orprocessors. Per numeral 937, the system then proceeds to find pertinentdata from the retrieved instance of the template to modify and/or use toassign nozzle firing decisions to mitigate error. Per numerals 938-941,and as discussed previously, in an embodiment where the template takesthe form of a bitmap of nozzle firing data, the system can base erroradaptation to a “closest” pixel in the template to an error vectorposition, a weighted measure of multiple pixels from the template, or insome other manner. Per numeral 940, an affine transform can be applied,with a process essentially performing matrix math on a “tile” of printgrid points in order to obtain new firing decisions; for example, such atransform can weight template data by offset, rotation and other factorsto obtain data for “transformed space” corresponding to true substrateposition (and orientation, skew, etc.). Other processes can also beperformed, per numeral 941. With nozzle assignments made, the system canthen also optionally invoke post-position compensation processing inorder to rectify fill or ink density errors for discrete areas of thesubstrate. Several options and types of processing are represented inFIG. 9C (these will also be discussed generally below in connection withFIGS. 10A-E). For example, numeral 951 illustrates a hypotheticalfluidic well that will hold a light generating element of an OLEDdisplay panel, overlaid by the print grid 953, and with a particularnode or droplet position indicated by numeral 954. If positional errorresults in too many or too few droplets within the confines of well 951,an antialiasing process can be applied to check the number of dropletsthat will fall within the well; for example, it could be that rotationof the print grid changes the number of droplets that will fall withinthe well given a droplet density represented by the template—theantialiasing process detects this issue and modifies (945) nozzleassignments from the position compensation process so that the correctnumber and/or volume of droplets will be deposited within the well. Asindicated at the right side of the FIG., via numerals 946-948, dropletparticulars and/or nozzle validation can be factored into this processas well. For example, if the droplet for node 954 has stored dropletparameters indicating positional error (e.g., the expected firingtrajectory has error α, β which would cause the droplet to land outsidethe depicted fluidic well), this issue can also be corrected (945) bysoftware, which examines particulars for other “nodes” which fall withinthe well to determine which ones should have firing decisions changed soas to meet required fill parameters. Similarly, if a validation processis used and a firing decision is assigned by the position compensationprocess to an inoperative (or disqualified) nozzle, this issue can bedetected and corrected (945) by software. As noted earlier, in stillanother embodiment, droplet parameters can be measured in situ, andperiodically updated, to provide a robust, current data set thataccounts for changing conditions. Generally speaking, step 945 correctsfor fill and aliasing errors, to ensure that liquid delivery will meetrequired particulars for deposition. If there is an error that cannot beaddressed or accounted for, detected per process 955, then an exceptionhandling routine (957) is called, typically to adjust or recompute scanpaths so as to address the error in question, or to newly render data.If errors have then been fully mitigated, output data is then storedand/or sent to the printer and printhead as appropriate, per numeral959. Note that in one embodiment, system software further detectsrepeated error that is correlated among substrates, and it can thenoptionally update the cached template (i.e., per 961) to “learn” therepeatable error and adapt the template to that error. For example, itcould be that positional error is caused in a given system by anunintended protrusion in a system edge guide for the substrate, whichcauses a substrate to “lurch” slightly at a particular position in itsmotion or relative to a specific position; these and other repeatableerrors can be learned by the system and used to reduce per-job errorprocessing. This technique will be further discussed below in connectionwith FIG. 10E.

FIGS. 10A-10E are used to show different types of error compensationtechniques that can be applied, i.e., variously in the assignment ofnozzle firing decisions, in the adjustment of droplet particulars for aparticular node of the print grid, and/or as a post-positioncompensation process.

More particularly, FIG. 10A shows a flowchart 1001 relating to dropletassignment and/or droplet adjustment in a region; for example, such atechnique can be applied to halftoning on a localized basis (i.e., todeposit fluid that will spread to provide blanket coverage at acalibrated thickness), or to an aggregate fill within a fluidic well(e.g., as discussed above in connection with FIG. 9C). The method firstidentifies the region or well in question, per numeral 1003, and thedesired number of droplets or desired fill volume. Per numeral 1005, thesystem then retrieves statistical mean and variance of dropletparameters for each nozzle and/or nozzle drive waveform; this dataprovides an understanding of expected droplet parameters with a degreeof confidence. Note that as represented by the parameters ν, α and β, inone embodiment, the system retrieves from memory parameters representingexpected droplet volume and expected two-dimensional droplet landingposition, as well as variance of these parameters. System software thenproceeds to simulate the fill to determine whether expected ink density(or aggregate volume) meets predetermined thresholds; in one embodiment,the system simply determines eligible combinations of droplets needed tomeet the predetermined thresholds and it then selects one of theseeligible combinations (i.e., in a manner which optimizes the ability todo this simultaneously for multiple regions in a scan-swath traversed bythe printhead(s)). In another embodiment, the system simply selects anumber of droplets and then post-adjusts the combination of droplets ifthat combination would be expected to produce a result outside of thepredetermined threshold. Per numerals 1006, 1007 and 1008, the systemcan in one embodiment select a different drive waveform for a givennozzle (e.g., one of sixteen preprogrammed waveforms as describedearlier), or it can select a different nozzle, or check to see whether aspecific nozzle is available. Per numeral 1009, the system adjustsnozzle assignments (including drive waveform selection information) asnecessary, and the print process is then again scrutinized for error(1011, e.g., suitability of predetermined scan paths and number ofscans). If there is an error, the system can adjust the printhead offsetfor a given scan path (1012) and/or adjust the number of scans (1013).If there is no error, the method ends (1014) with assigned data beingoutput to the printer as previously discussed.

FIG. 10B provides another flowchart 1021 relating to templateadjustment, this time as a post-error correction step. Per numeral 1023,for each of N regions or fluidic wells, system software proceeds toidentify well position, for example, based on the detected error data.At step 1025, the software reviews the firing decisions for print gridnodes falling within the region of interest, and retrieves a mean (μ)and standard deviation or other spread measure (e.g., σ) for each suchparameter (1026). Following a simulation (1027) of aggregate volume forthe region, or volume distribution, the system then determines whetherthis volume or distribution conforms to predetermined thresholds, forexample, a minimum threshold (Th1) and a maximum threshold (Th2), pernumerals 1029 and 1031. If the volume or distribution does not conformto the predetermined thresholds, then the system software proceed toadjust droplet and/or waveform assignments, as indicated by numerals1033, 1035 and 1036, until the volume or distribution does conform tothe predetermined thresholds. In one embodiment, because multiplewaveforms are available for each nozzle and have been selected inadvance to produce deliberate variation in droplet volume, error can becompensated for without changing scan path simply by assigning a newfiring waveform to the particular print grid node; if this waveformdiffers from another firing decision for the same printhead nozzle, thenis up to the system to schedule selection of a different “default”waveform for the particular nozzle in between nozzle firings (see, i.e.,the “trigger (fire)” signal depicted in FIG. 5B). The system then savesthe pertinent nozzle data as appropriate, per numeral 1037. As noted byoptional process block 1039, if there is no suitable waveform which hasbeen programmed for a particular nozzle, in one embodiment, the systemcan at this time add a waveform or reprogram a selected waveform in anattempt to improve the firing particulars obtainable from a givennozzle.

FIG. 10C shows a flowchart 1041 of a process where nozzle/waveform datais factored into rendering of an instance of the template to account forsubstrate or panel error. More specifically, as indicated by numerals1043-1047, the system can retrieve nozzle drive particularscorresponding to a bitmap (e.g., the template in bitmap form). Forexample, again using an example where a new print grid node firingassignment is based on a weighted average of four print pixelscorresponding to a template, if the four assigned nozzles were expectedto produce 10.00, 10.50, 10.00 and 10.20 pL droplets, respectively, thenthis information can be taken into account and used to select either anozzle or a nozzle waveform to deposit droplets onto a misalignedsubstrate. Returning to the example of fluidic well 951 from FIG. 9C,any print grid nodes (e.g., 954) falling within the depicted well andassigned to fire can be potentially used to obtain an aggregate volumefor the fluidic well, and the system can effectively weight the fourprint pixels in this hypothetical and select a new grid point (e.g.,nozzle, or firing time) and associated drive waveform (if multiplewaveforms are available) to produce a droplet having expected volumeparameters corresponding to the weighted combination of the four printpixels. Per numeral 1049, the software can apply any smoothing asdesired (e.g., adjustment of neighboring print pixels or ensuing dropletselection as necessary) and, once again, write output data (including aselected drive waveform) to memory; this output data will then beultimately sent to the printer to control printing. Per numeral 1053,the system can assume a fixed scan pattern (i.e., and simply assignnozzles and drive waveforms in a manner to address error) or, in anotherembodiment, it can revisit and re-optimize scanning (rasterization), forexample, by changing scan paths, printhead offsets, the number of scans,or other particulars, all with an eye toward minimizing printing time;these optional features are represented by numerals 1055 and 1057.

FIG. 10D shows yet another flowchart 1061, relating to halftone (i.e.,drop density) adjustment. In connection with this embodiment, it shouldbe assumed that it is desired to control the ink drop density, forexample, to provide blanket coverage over a region of the substrate withdeposited ink, but such that the ink droplets are deposited with adensity that imparts a desired layer thickness (i.e., given limitedspreading characteristics of each droplet). Such a process is especiallyuseful to creating barrier layers, encapsulation layers or other layerswhere it is desired that layer thickness be consistent over a relativelylarge area. Per numeral 1063, once again, it is assumed that someportion of data from the template is to be rendered to compensate forsubstrate and/or panel positional error. Per numerals 1067, 1069 and1071, the software in this embodiment retrieves expected droplet volume,position and variance and desired layer parameters (e.g., such asthickness and halftone density or ink density needed to produce thedesired thickness). The system then selects nozzles and drive waveformsfrom an available pool (e.g., nozzles that will pass over the particulararea assuming a particular scan path), in a manner calculated to promotethe same ink density represented by the original template data. Forexample, if it is desired to produce a five micron thick encapsulationlayer, the system (a) identifies nozzles that will pass over each area,desired ink density needed to produce the desired thickness, per-nozzleand per-waveform droplet particulars, (b) applies a mathematicalfunction to select nozzles and drive waveforms that will produce thedesired density (i.e., which is then rolled into nozzle selection foradjacent regions as well), and it then outputs printer control data.Note that in planning a halftone or density pattern, the system softwaretypically takes care to plan depositions to deposit an even density offluid, e.g., balancing “heavy” droplets (e.g., 11.00 pL) with “light”droplets (e.g., 9.00 pL) in terms of droplet distribution if aconsistent volume (e.g., 10.00 pL) is unavailable given nozzleparticulars. Once again, per numeral 1073, the output particulars areonce again scrutinized for error (e.g., inability of a scan path toproduce required results) and, if no error is found, data is output tothe printer (1075) or conversely, if error is found, an exceptionprocess is called (1077, e.g., to reassess rasterization). Otheralternatives will occur to those skilled in the art.

Finally, FIG. 10E provides a flowchart 1081 relating to updating thestored template for repeatable error, e.g., as introduced above inconnection with FIG. 9C. For each new substrate, the depicted methodcompares deviation from expected position (1083) with past errors, whichhave been stored in memory per numeral 1085. The system softwareattempts to detect correlation in the error (e.g., as opposed to uniquesubstrate error), per numeral 1087. Per numerals 1088-1090, the degreeof correlation sought can be based on some sort of calibration (i.e., toset an expected substrate norm), the continual monitoring of fiducialsfor successive substrates, or based on dead reckoning). The systemeffectively “learns” patterns in the errors, for example, based onregression software, a neural net or other adaptive process, and it thenmodifies the template as appropriate and updates a history of deviationdata, per numerals 1091 and 1093. Finally, per numeral 1095, thesoftware corrects the current substrate for any uncorrected error (e.g.,unique error) and outputs data to the printer as has previously beendescribed.

As noted earlier, it is generally desired to perform printing quickly,so as to minimize processing time and increase throughput; in oneembodiment, a substrate that is on the order of two meters wide and longcan have a layer deposited uniformly over its surface in less than 90seconds per layer; in another embodiment, this time is 45 seconds orless. It is therefore advantageous in such an application that renderingand per-substrate (or per product) error mitigation be performed asrapidly as possible.

FIGS. 11A-11B are used to introduce a parallel processing architectureto facilitate this processing speed. As should be apparent, withprecision manufacturing (e.g., printing a layer of many TV screens atone, each having millions of pixels), software adjustment of a detailedprint grid to generate printer control data could take several seconds.The architecture and processes presented in FIGS. 11A-11B are used toreduce this time, ideally to two seconds or less.

More particularly, as represented in FIG. 11A, a copy of a cached printimage, stored recipe data or other pertinent source data representingideal printing is first retrieved. A master or supervisory processor1103 would have already been made aware of any substrate configurationdata, and so would have an understanding of the number of products(panels) and their respective expected locations. The supervisoryprocessor 1103 receives alignment data and computes error (e.g., foreach panel or product on an independent basis). Panel processing, orerror compensation at a sub-panel level is optional, i.e., the disclosedtechniques can be applied even where an instance of the print image isconformed on a basis that is linear throughout the specific substrate.The system also includes a set of parallel processors 1105, in oneembodiment, a multicore processor or a graphics processing unit (GPU). AGPU typically includes a large number of cores 1107 (e.g., hundreds tothousands), each of which is (or many of which are) utilized in thisembodiment to perform processing in parallel. The supervisory processor1103, dependent on panel definition, desired error correction and otherfactors, makes a decision as to how many parallel threads or processesshould be used to perform transformation of the instance of the templateprint image. In connection with this process, the supervisory processorsubdivides the overall print area for the substrate as appropriate,assigns any pertinent transformation parameters to the pertinent core orprocessor, and stores (caches) the instance of the template print imagein an embedded DRAM 1109. Note that the embedded DRAM advantageouslyincludes multiple banks, ports or arrays 1111, each having a register1111A used by one or more of the cores 1107 for error correction andrendering of printer control data (including transformation and overlayof any source data). The embedded memory is advantageously structuredfor parallel access such that accesses by one core or processor do notlimit bandwidth of another core or processor. To this effect, thearchitecture can feature an ultra-wide access path 1113 (e.g., featuringhundreds of data access lines, as appropriate) such that each core canaccess memory 1109 in parallel. Note that, in one implementation, themanner of storing the source data is dependent on processor or coreassignment, such that each core or processor has access to the data itneeds for transformation and to a write area for transformed printercontrol data. In one contemplated implementation, the supervisoryprocessor 1103 does not necessarily use every available core orprocessor, but assigns cores or processors to handle discrete products(e.g., panels) or mutually exclusive parts of a panel or product. Forexample, if a hypothetical panel has 15 panels and the system includes31 parallel processing units, the supervisory processor might assign 2parallel processing units, each unit to process one half of a panel. Thesupervisory processor would direct portions of the template to embeddedDRAM for storage as appropriate, would write any transformationparameters (e.g., skew algorithm) into the pertinent registers 1111A foreach memory bank or array (i.e., for each core or parallel processor)and would then await a signal form each core or processor that itsprocessing is complete. The output is then a transformed per-substrateset of printer control data, distorted to adapt printing to anyper-substrate or per-product variations, to precisely place theto-be-deposited layer of material in question. Note that as representedby numerals 1115 and 1117, each of the supervisory processor and therespective cores or processors are governed by instructions stored onnon-transitory machine-readable media that control the respectivesupervisory processor, core or processor to perform specific processingfunctions, as has been described earlier. Also, note that the embeddedDRAM can be designed to provide a form of direct memory access (DMA),such that rendered data can be written to memory by one processor core(as available) and unloaded by independent means (i.e., while the oneprocessor core proceeds to adjust other data to correct for positionalerror).

FIG. 11A shows a number of additional implementation options at theright side of the FIG. First, as noted earlier, each panel can beassigned to one or more respective cores or processors, as representedby numeral 1119. As in a typical manufacturing process, sequences ofsubstrates will use the same recipe or template, the configurationrepresented by option 1119 is typically a fixed cost (e.g., thesupervisory processor 1103 typically does not need to recomputeassignments or change data storage parameters for respective substrates.Second, per numeral 1120, given this fixed assignment, the supervisoryprocessor can optionally assign respective transformations per core;while the examples above generally separately discuss offset, rotation,scale and skew corrections, in a typical implementation, transformationcan be complex, involving any combination of these corrections, asappropriate. The supervisory processor computes the pertinenttransformation and then assigns the computed transformation to theproper processor or core, which then executes his transformation on allaffected template data which it has been assigned. As represented bynumeral 1120, in one embodiment, each transformation is provided to arespective processor(s) or core(s). Per numeral 1123, in one embodiment,storage of pre-processed template data or transformed data can bestriped. That is to say, it was earlier noted that a transformation mayinvolve weighting of firing decisions four overlapping pixels on a(translated) print image or print image data representing a panel. Perthe option represented by numeral 1123, print image pixel data can bestore in a manner conducive for this processing, such as by storingnorthwest, northeast, southwest and southeast pixel data in the samememory row, in respective memory arrays (but at the same address) or inanother manner. There exist many possible memory storage techniques thatcan be used to speed data retrieval and processing (for example, as isconventionally done for graphics and game process to speed imagerendering). The same types of memory processes can be employed for thisembodiment. As also represented by numeral 1123, in one embodiment, avariable (per memory array) column offset can be used, e.g., such that,if print pixel data is stored within a given row, the system canautomatically and speedily fetch the next set of data needed forprocessing. As an example, the cached print image data can be stored inDRAM (1111) in a striped manner (e.g., a row in each of two memoryarrays) with column offsets used to retrieve the pertinent print pixelinformation for both memory arrows on an incrementing basis. Manyalternatives and variations to this processing are also possible.

Note that the configuration just described is not the only one possible.For example, instead of assigning geographies of the substrate to eachcore, the supervisory processor or other master 1103 can split thetransform math, assigning different processes to respective cores(1121). In one embodiment, one core could be assigned to perform onetask associated with an affine transform, while a different core couldbe assigned to perform another. As indicated by numeral 1122, nearly anyallocation of responsibilities can be affected amongst the multiplecores, whether parallel or sequential; as it is generally desired todetect per-substrate or per-panel error and proceed with printing asquickly as possible, so as to maximize manufacturing throughput, anyefficiency in speeding can potentially be applied to multiple availableprocessor or cores if it fulfils this goal.

FIG. 11B shows a flowchart 1151 associated with a run-time process. Inthis example, it will be assumed that multiple cores are each assigned,once error has been measured, to apply one or more affine transforms torespective geographies of the overall print area (i.e., of thesubstrate). As indicated by numeral 1153, template data is first loadedor cached. The supervisory processor makes use of such source data asappropriate (1155) to identify pertinent alignment marks or fiducials(1157), and it then directs the printer camera system to the appropriaterough coordinates. The printer camera system returns precise measurementinformation, which the supervisory processor meters against the obtainedsource information 1155. The supervisory processor then performs paneland/or substrate transformation calculation as appropriate (1159), inview of detected geography, and it then apportions processing ranges andtransform parameters to each core, processor or parallel processingthread as appropriate (1161 and 1163). For a repeated substrate recipe,the supervisory processor could automatically parse subsets of thereceived template image into memory dedicated to specific cores,processors or threads. Each core, processor or thread then beginstransforming (1165) its assigned data, to convert or distort thetemplate in a manner to conform print particulars to detected substrateor panel geography. As part of this process, reasonably up-to-date printnozzle and/or droplet data is made available (1167) to ensure thatfinished, transformed printer control data will provide for accuratedeposition, given any printhead, droplet or nozzle particulars. Notethat, in other embodiments, this adjustment (i.e., dependent on printnozzle particulars) can be made by a dedicated core, processor or thread(i.e., separate from cores, processors or threads performing print gridoperations) or can be performed by the supervisory processor. Once anytransformation has been performed, consistent withnozzle/droplet-specific characteristics, the transformed printer controldata can be unloaded form memory, rasterized (1169) and sent to theprinter with appropriate instructions for printing (1171).

Reflecting on the various techniques and considerations introducedabove, a manufacturing process can be performed to mass produce productsquickly and at low per-unit cost. Applied to display device manufacture,e.g., flat panel displays, these techniques enable fast, per-panelprinting processes, with multiple panels optionally produced from acommon substrate. By providing for fast, repeatable printing techniques(e.g., using common inks and printheads from panel-to-panel), it isbelieved that printing can be substantially improved, for example,reducing per-layer printing time to a small fraction of the time thatwould be required without the techniques above, all while guaranteeingper-target region fill volumes are within specification. Again returningto the example of large HD television displays, it is believed that eachcolor component layer can be accurately and reliably printed for largesubstrates (e.g., generation 8.5 substrates, which are approximately 220cm×250 cm) in one hundred and eighty seconds or less, or even ninetyseconds or less, representing substantial process improvement. Improvingthe efficiency and quality of printing paves the way for significantreductions in cost of producing large HD television displays, and thuslower end-consumer cost. As noted earlier, while display manufacture(and OLED manufacture in particular) is one application of thetechniques introduced herein, these techniques can be applied to a widevariety of processes, computer, printers, software, manufacturingequipment and end-devices, and are not limited to display panels. Inparticular, it is anticipated that the disclosed techniques can beapplied to any process where a printer is used to deposit a layer ofmultiple products as part of a common print operation, including withoutlimitation, to any microelectronics, microoptical or “3D printing”application.

Note that the described techniques provide for a large number ofoptions. In one embodiment, panel (or per-product) misalignment ordistortion can be adjusted for on a product-by-product basis within asingle array or on a single substrate. A printer scan path can beplanned with ensuing adjustment/adaptation based on one or morealignment errors, such that a scan path traversing two panels hasdifferent firing instructions for each substrate, notwithstanding commonprint data (e.g., rotation or adjustment of data for one panel can varyfrom print job to print job). Optionally, this information can beadjusted from a source template (e.g., a bitmap representing binaryfiring decisions), in real time. In other embodiments, print area and/orscan paths can be added or completely replanned from substrate tosubstrate, notwithstanding common printer source data. The describedtechniques can be used to fabricate OLED panels, for example, 2, 4, 6,or a different number of panels as part of a single print job. Followingfabrication, these panels can be separated and applied to respectiveproducts, e.g., to fabricate respective HDTV displays or other types ofdevices. By performing fine alignment in software (e.g., sub-millimeteralignment), the disclosed techniques provide for more accurate productfabrication with less emphasis on precision mechanical positioning andaccurate placement and alignment of deposited errors, in a mannerconforming to underlying per-product or per-substrate misalignment ordeformities.

The foregoing description and in the accompanying drawings, specificterminology and drawing symbols have been set forth to provide athorough understanding of the disclosed embodiments. In some instances,the terminology and symbols may imply specific details that are notrequired to practice those embodiments. The terms “exemplary” and“embodiment” are used to express an example, not a preference orrequirement.

As indicated, various modifications and changes may be made to theembodiments presented herein without departing from the broader spiritand scope of the disclosure. For example, features or aspects of any ofthe embodiments may be applied, at least where practical, in combinationwith any other of the embodiments or in place of counterpart features oraspects thereof. Thus, for example, not all features are shown in eachand every drawing and, for example, a feature or technique shown inaccordance with the embodiment of one drawing should be assumed to beoptionally employable as an element of, or in combination of, featuresof any other drawing or embodiment, even if not specifically called outin the specification. Accordingly, the specification and drawings are tobe regarded in an illustrative rather than a restrictive sense.

We claim:
 1. A method of fabricating a flat panel device, the methodcomprising: receiving a first substrate; using a printer to print aliquid onto the first substrate, the liquid carrying a material thatwill form a permanent layer of the flat panel device; and processing theliquid to form the permanent layer therefrom; wherein (a) the methodfurther comprises detecting position of a fiducial on the firstsubstrate and detecting error dependent on difference between theposition of the fiducial and an expected feature position, (b) using theprinter comprises receiving stored data defining where the permanentlayer for the flat panel device is to be printed, rendering the storeddata according to the error, to generate adjusted data, and printingdroplets of the liquid onto the first substrate according to theadjusted data, and (c) rendering the stored data further comprisesassigning individual nozzles of a printhead of the printer to depositrespective droplets of the liquid in a specific region of the firstsubstrate, in dependence on the error, in a manner where a targetaggregate volume of the liquid deposited in the specific region isrestricted to fall within a predetermined error threshold relative to adesired amount volume of the liquid for the specific region.
 2. Themethod of claim 1, wherein: the substrate represents respective productsto be fabricated in parallel on the first substrate, the flat paneldevice being one of the respective products; using the printer to printincludes using the printer to print as part of an integral print tofabricate a permanent layer of each of the respective products on thefirst substrate; and the method further comprises, following using theprinter to print, separating the flat panel device from the otherrespective products on the first substrate.
 3. The method of claim 2,wherein each of the respective products is an organic light emittingdiode display device, and wherein the using the printer comprisesprinting the droplets of the liquid onto the substrate using a dropletdensity selected in dependence on desired thickness of the permanentlayer for the respective products.
 4. The method of claim 2, embodied asa method of making a display for a flat panel television.
 5. The methodof claim 2, wherein: the fiducial comprises a first visible feature, thestored data is first stored data, the error is a first error, theadjusted data is first adjusted data, and the first visible feature isassociated with the flat panel device but is not associated with atleast another one of the respective products; the method furthercomprises optically detecting position of a second visible feature onthe first substrate and detecting second error between the position ofthe second visible feature and an expected feature position, the secondvisible feature being associated with the other one of the respectiveproducts but not with said flat panel device; and using the printercomprises receiving second stored data that defines where the permanentlayer corresponding to the other one of the respective products is to befabricated, rendering the second stored data according to the seconderror, to generate second adjusted data, and printing onto the firstsubstrate according to the second adjusted data, such that liquid forthe permanent layers respective to each of the flat panel device and theother one of the respective products is printed on the first substratein a manner dependent on the first error and the second error,respectively.
 6. The method of claim 5, wherein the using the printercomprises printing according to a scan path representing substantiallycontinuous relative motion between the printhead and the firstsubstrate, the scan path to deposit droplets of the liquid to form atleast a portion of the permanent layers respective to each of the flatpanel device and the other one of the respective products, such thatprinting according to the scan path is performed in dependence on eachof the first error and the second error, dependent on whether the scanpath is then-traversing a location associated with the permanent layerrespective to the flat panel device or the permanent layer respective tothe other one of the respective products.
 7. The method of claim 2,wherein the using the printer comprises printing according to a scanpath representing substantially continuous relative motion between theprinthead and the first substrate, the scan path to deposit droplets ofthe liquid to form at least a portion of the layer respective to theflat panel device and a layer respective to another one of therespective products, such that printing according to the scan path isperformed for each of the layer respective to the flat panel device andthe layer respective to the other one of the respective products in atleast partial dependence on the error.
 8. The method of claim 2,wherein: the fiducial is a first visible feature, the stored data isfirst stored data, the error is a first error, the adjusted data isfirst adjusted data, and the first substrate comprises visible featuresat respective locations on the first substrate, the visible featuresincluding the first visible feature; the method further comprisesoptically detecting each of the visible feature, and detecting errorbetween a corresponding position of the feature and at least oneexpected feature position; and using the printer comprises receivingstored data that defines where the permanent layer for each of therespective products is to be printed, rendering the stored data thatdefines where the permanent layer for each of the respective products isto be fabricated according to one or more of the errors, the dependenceon the one or more of the errors for each of the respective productsbeing dependent on position of the respective product on the substrate,relative to the visible features, to generate per-product adjusted data,and printing the liquid for each of the respective products according tothe per-product adjusted data.
 9. The method of claim 8, at leastpartially embodied in a parallel processing environment, whereinrendering comprises, for each of multiple processor cores, selecting arespective subset of print area of the first substrate and assigning therespective subset to the one of the multiple processor cores, andgenerating the per-product transformed data using the selected ones ofthe multiple processor cores.
 10. The method of claim 9, whereinselecting is performed in a manner where, for each one of the respectiveproducts, multiple processor cores are assigned to render print data independence on detected error in a manner in a manner that is unique tothe one of the respective products.
 11. The method of claim 1, whereinthe stored data comprises a first bitmap having pixels that representprinthead nozzle firing decisions at respective positions, and wherein:rendering the stored data includes generating a second bitmap alsohaving pixels that represent nozzle firing decisions at respectivepositions and, for each given pixel of the second bitmap, identifying atleast one pixel of the first bitmap dependent on the error, andgenerating a corresponding nozzle decision for the given pixel of thesecond bitmap dependent on the identified at least one pixel of thefirst bitmap; and wherein using the printer further comprises printingthe liquid onto the first substrate according to the second bitmap. 12.The method of claim 1, wherein the stored data comprises first grayscaledata having pixels, each of the pixels represented as a multi-bit valuethat represents desired volume of the liquid at a respective positionrelative to the first substrate, and wherein: rendering the stored dataincludes generating second grayscale data having pixels, each of thepixels of the second grayscale data represented as a multi-bit valuethat represents desired volume of the liquid at a respective position onthe first substrate, identifying for each of the pixels of the secondgrayscale data at least one grayscale value of the first grayscale data,dependent on the error, and generating the multi-bit value for each ofthe pixels of the second grayscale data dependent on the identifiedleast one grayscale value of the first grayscale data; and wherein usingthe printer further comprises printing the liquid according to thesecond grayscale data.
 13. The method of claim 12, wherein rendering thestored data further comprises converting the multi-bit values of thesecond grayscale data to a droplet density, the droplet density selectedto produce a volume of the liquid that locally varies according to thegrayscale values of the second grayscale data, and wherein using theprinter comprises printing the liquid according to the flat panel deviceaccording to the selected droplet density.
 14. The method of claim 1,wherein the stored data defines a predetermined number of raster scansbetween a printhead and the first substrate, and for each respectiveraster scan, a predetermined cross-scan position of the printhead, andwherein: using a printer to print the liquid onto the first substrateincludes using the predetermined number or raster scans and associatedcross-scan positions, but using the individual nozzles of the printheadselected in dependence on the error
 15. The method of claim 1, whereinthe error represents at least one of skew, an angle of rotation, adistance value, or an amount of scaling, and wherein using the printercomprises printing the liquid onto the first substrate in a manneradjusted to mitigate the at least one.
 16. The method of claim 1,wherein receiving the first substrate includes performing roughmechanical alignment of the first substrate relative to the printer, andwherein using the printer comprises using the error to perform insoftware a sub-millimeter fine alignment of printer data relative to anexpected alignment of the first substrate.
 17. The method of claim 1,wherein using the printer and processing the liquid to form thepermanent layer respectively comprise printing the liquid and curing theliquid in a common, controlled atmosphere, the printing and curingcollectively uninterrupted by exposure to an uncontrolled atmosphere.18. The method of claim 1, at least partially embodied in a parallelprocessing environment, wherein rendering comprises selecting a specificprocessor core of multiple processor cores, assigning a transformationfunction and a subset of print area of the substrate to the specificprocessor core, and using the specific processor core to generate theadjusted data.
 19. The method of claim 1, at least partially embodied ina parallel processing environment, wherein rendering comprises selectingfor each core of multiple processor cores, and a respective subset ofprint area of the substrate, and generating a print image usingaggregated outputs of the multiple available processor cores, the printimage having pixels that each represent a nozzle firing decision at arespective area of the substrate.
 20. The method of claim 1, wherein:rendering further comprises receiving empirical measurement data foreach given of the nozzles of the printhead representing a parameter of adroplet expected to be produced from the given one of the nozzles, theparameter representing at least one of droplet volume, droplet velocity,droplet trajectory or expected droplet landing position; assigningindividual nozzles of a printhead of the printer to deposit respectivedroplets of the liquid in a specific region of the first substrate, independence on the error, is performed in dependence on the empiricalmeasurement data; and assigning individual nozzles of a printhead of theprinter to deposit respective droplets of the liquid in a specificregion of the first substrate, in dependence on the error, furthercomprises assigning firing decisions in dependence on the error,determining an expected volume of the liquid to be deposited in view ofthe assigned firing decisions, comparing the expected volume of theliquid to be deposited with at least one threshold, and adjusting theassigned nozzle firing decisions if the expected volume violates the atleast one threshold.
 21. The method of claim 20, wherein the at leastone threshold comprises a maximum volume of the liquid to be depositedin the specific region and a minimum volume of the liquid to bedeposited in the specific region, and wherein adjusting comprisesproducing nozzle firing decisions such that the expected volume of theliquid is not less than the minimum volume and is not more than themaximum volume.
 22. The method of claim 20, wherein the liquid is toform a light generating layer of an organic light emitting diode as thepermanent layer of the flat panel device.
 23. An apparatus to fabricatea flat panel device, the apparatus comprising: means for receiving afirst substrate; means for printing a liquid onto the first substrate,the liquid carrying a material that will form a permanent layer of eachone of respective products to be fabricated in parallel on the firstsubstrate, the flat panel device being one of the respective products,wherein printing is performed as part of an integral print process forthe permanent layer of each of the respective products on the firstsubstrate; means for, following printing of the liquid, processing theliquid to form a permanent layer of each of the respective products; andmeans for, following the processing, separating the flat panel devicefrom the other respective products on the first substrate; wherein (a)the apparatus further comprises means for detecting position of afiducial on the first substrate and detecting error dependent ondifference between the position of the fiducial and an expected featureposition, (b) the means for printing comprises means for receivingstored data defining where the permanent layer corresponding to the flatpanel device is to be printed, and means for rendering the stored dataaccording to the error, to generate adjusted data, wherein printing ontothe first substrate is performed according to the adjusted data, and (c)the means for rendering further comprises means for assigning individualnozzles of a printhead of the printer to deposit respective droplets ofthe liquid in a specific region of the first substrate, in dependence onthe error, in a manner where a target aggregate volume of the liquiddeposited in the specific region is kept within a predetermined errorthreshold relative to a desired amount volume of the liquid for thespecific region.
 24. An apparatus to fabricate a flat panel device, theapparatus comprising: a mechanical handler to receive a first substrate;and a printer to print a liquid comprising a material that will formpermanent layers of respective products on the first substrate, the flatpanel device being one of the respective products, wherein the printeris to print the permanent layers of the respective products on the firstsubstrate as part of an integral print process; and a cure mechanism tocure the material so as to form the permanent layers; wherein the flatpanel device is to be separated, following print of the permanentlayers, from the other respective products on the first substrate, theapparatus further comprises a detection device to detect position of afiducial on the first substrate and to detect error dependent ondifference between the position of the fiducial and an expected featureposition, and at least one processor, the at least one processor is toreceive data defining where the permanent layer corresponding to theflat panel device is to be printed, render the data according to theerror, to generate adjusted data, cause the printer to print onto thefirst substrate according to the adjusted data; and wherein the at leastone processor is further to assign individual nozzles of a printhead ofthe printer to deposit respective droplets of the liquid in a specificregion of the first substrate, in dependence on the error, in a mannerwhere a target aggregate volume of the liquid deposited in the specificregion is kept within a predetermined error threshold relative to adesired amount volume of the liquid for the specific region, in order togenerate the adjusted data.
 25. An apparatus comprising instructionsstored on non-transitory machine-readable media, the instructions to beexecuted by at least one processor of an apparatus comprising amechanical handler to receive a first substrate, a printer to print theliquid onto the first substrate, a cure mechanism to cure the liquid soas to form a permanent layer of a flat panel device, and a detectiondevice to detect position a fiducial on the first substrate, theinstructions when executed to cause the machine to: detect errordependent on difference between the position of the fiducial and anexpected feature position; receive data defining where the permanentlayer corresponding to the flat panel device is to be printed on thefirst substrate; render the data according to the error, to generateadjusted data; and cause the printer to print onto the first substrateaccording to the adjusted data; wherein the instructions when executedare further to cause the at least one processor to assign individualnozzles of a printhead of the printer to deposit respective droplets ofthe liquid in a specific region of the first substrate, in dependence onthe error, in a manner where a target aggregate volume of the liquiddeposited in the specific region is kept within a predetermined errorthreshold relative to a desired amount volume of the liquid for thespecific region, in order to generate the adjusted data.